Organization And Basis of Presentation (Policy)	12 Months Ended
Dec. 31, 2012
Policy Text Block [Line Items]
Organization	Nature of Operations and Basis of Consolidation. Duke Energy Corporation (collectively with its subsidiaries, Duke Energy), is an energy company headquartered in Charlotte, North Carolina. Duke Energy operates in the United States (U.S.) and Latin America primarily through its direct and indirect subsidiaries. Duke Energy's subsidiaries included Duke Energy Carolinas, LLC (Duke Energy Carolinas), Duke Energy Ohio, Inc. (Duke Energy Ohio), which includes Duke Energy Kentucky, Inc. (Duke Energy Kentucky), and Duke Energy Indiana, Inc. (Duke Energy Indiana) prior to the merger with Progress Energy, Inc. (Progress Energy). On July 2, 2012, Duke Energy merged with Progress Energy, with Duke Energy continuing as the surviving corporation, and Progress Energy becoming a subsidiary of Duke Energy. Carolina Power & Light Company d/b/a Progress Energy Carolinas, Inc. (Progress Energy Carolinas) and Florida Power Corporation d/b/a Progress Energy Florida, Inc. (Progress Energy Florida), Progress Energy's regulated utility subsidiaries, are now indirect subsidiaries of Duke Energy. Duke Energy's consolidated financial statements include Progress Energy, Progress Energy Carolinas and Progress Energy Florida activity beginning July 2, 2012. See Note 2 for additional information regarding the merger. When discussing Duke Energy's consolidated financial information, it necessarily includes the results of its six separate subsidiary registrants, Duke Energy Carolinas, Progress Energy, Progress Energy Carolinas, Progress Energy Florida, Duke Energy Ohio and Duke Energy Indiana (collectively referred to as the Subsidiary Registrants), which, along with Duke Energy, are collectively referred to as the Duke Energy Registrants. Progress Energy, Progress Energy Carolinas and Progress Energy Florida (collectively referred to as the Progress Energy Registrants) continue to maintain reporting requirements as SEC registrants. In accordance with SEC guidance, the Progress Energy Registrants did not reflect the impacts of acquisition accounting from the merger with Duke Energy, whereby the adjustments of assets and liabilities to fair value and the resultant goodwill would be shown on the financial statements of the Progress Energy Registrants. These adjustments were recorded by Duke Energy. The information in these combined notes relates to each of the Duke Energy Registrants as noted in the Index to the Combined Notes. However, none of the registrants makes any representation as to information related solely to Duke Energy or the subsidiaries of Duke Energy other than itself. As discussed further in Note 3, Duke Energy operates three reportable business segments: U.S. Franchised Electric and Gas (USFE&G), Commercial Power and International Energy. The remainder of Duke Energy's operations is presented as Other. These Consolidated Financial Statements include, after eliminating intercompany transactions and balances, the accounts of the Duke Energy Registrants and all majority-owned subsidiaries where the respective Duke Energy Registrants have control and those variable interest entities (VIEs) where the respective Duke Energy Registrants are the primary beneficiary. These Consolidated Financial Statements also reflect the Duke Energy Registrants' proportionate share of certain generation and transmission facilities. In January 2012, Duke Energy Ohio completed the sale of its 75% ownership of the Vermillion Generating Station (Vermillion); upon the close, Duke Energy Indiana purchased a 62.5% interest in the station. See Note 2 for further discussion. Duke Energy Carolinas, a wholly owned subsidiary of Duke Energy, is an electric utility company that generates, transmits, distributes and sells electricity in North Carolina and South Carolina. Duke Energy Carolinas is subject to the regulatory provisions of the North Carolina Utilities Commission (NCUC), the Public Service Commission of South Carolina (PSCSC), the U.S. Nuclear Regulatory Commission (NRC) and the Federal Energy Regulatory Commission (FERC). Substantially all of Duke Energy Carolinas' operations are regulated and qualify for regulatory accounting treatment. As discussed further in Note 3, Duke Energy Carolinas' operations include one reportable business segment, Franchised Electric. Progress Energy, a wholly owned subsidiary of Duke Energy, is a holding company headquartered in Raleigh, North Carolina, subject to regulation by the FERC. Progress Energy conducts operations through its wholly owned subsidiaries, Progress Energy Carolinas and Progress Energy Florida. As discussed further in Note 3, Progress Energy's operations include one reportable segment, Franchised Electric. Progress Energy Carolinas, an indirect wholly owned subsidiary of Duke Energy, is a regulated public utility primarily engaged in the generation, transmission, distribution and sale of electricity in portions of North Carolina and South Carolina. Progress Energy Carolinas is subject to the regulatory provisions of the NCUC, the PSCSC, the NRC and the FERC. Substantially all of Progress Energy Carolinas' operations are regulated and qualify for regulatory accounting treatment. As discussed further in Note 3, Progress Energy Carolinas' operations include one reportable segment, Franchised Electric. Progress Energy Florida, an indirect wholly owned subsidiary of Duke Energy, is a regulated public utility primarily engaged in the generation, transmission, distribution and sale of electricity in west central Florida. Progress Energy Florida is subject to the regulatory jurisdiction of the Florida Public Service Commission (FPSC), the NRC and the FERC. Substantially all of Progress Energy Florida's operations are regulated and qualify for regulatory accounting treatment. As discussed further in Note 3, Progress Energy Florida's operations include one reportable segment, Franchised Electric. Duke Energy Ohio, an indirect wholly owned subsidiary of Duke Energy, is a combination electric and gas public utility that provides service in the southwestern portion of Ohio and in northern Kentucky through its wholly owned subsidiary, Duke Energy Kentucky, as well as electric generation in parts of Ohio, Illinois and Pennsylvania. Duke Energy Ohio's principal lines of business include generation, transmission and distribution of electricity, the sale of and/or transportation of natural gas, and energy marketing. Duke Energy Ohio conducts competitive auctions for retail electricity supply in Ohio whereby the energy price is recovered from retail customers. Duke Energy Kentucky's principal lines of business include generation, transmission and distribution of electricity, as well as the sale of and/or transportation of natural gas. References herein to Duke Energy Ohio include Duke Energy Ohio and its subsidiaries, unless otherwise noted. Duke Energy Ohio is subject to the regulatory provisions of the Public Utilities Commission of Ohio (PUCO), the Kentucky Public Service Commission (KPSC) and the FERC. Duke Energy Ohio applies regulatory accounting treatment to substantially all of the operations in its Franchised Electric and Gas operating segment. Through November 2011, Duke Energy Ohio applied regulatory accounting treatment to certain rate riders associated with retail generation of its Commercial Power operating segment. See Note 3 for further information about Duke Energy Ohio's business segments. Duke Energy Indiana, an indirect wholly owned subsidiary of Duke Energy, is an electric utility that provides service in north central, central, and southern Indiana. Its primary line of business is generation, transmission and distribution of electricity. Duke Energy Indiana is subject to the regulatory provisions of the Indiana Utility Regulatory Commission (IURC) and the FERC. Substantially all of Duke Energy Indiana's operations are regulated and qualify for regulatory accounting treatment. As discussed further in Note 3, Duke Energy Indiana's operations include one reportable business segment, Franchised Electric. Certain prior year amounts have been reclassified to conform to current year presentation. In addition, prior year financial statements and footnote disclosures for the Progress Energy Registrants have been reclassified to conform to Duke Energy's presentation.
Reverse Stock Split	Reverse Stock Split. On July 2, 2012, just prior to the close of the merger with Progress Energy, Duke Energy executed a one-for-three reverse stock split with respect to the issued and outstanding shares of Duke Energy common stock. All per-share amounts included in this Form 10-K are presented as if the one-for-three reverse stock split had been effective from the beginning of the earliest period presented.
Use Of Estimates	Use of Estimates. To conform to generally accepted accounting principles (GAAP) in the U.S., management makes estimates and assumptions that affect the amounts reported in the Consolidated Financial Statements and Notes. Although these estimates are based on management's best available information at the time, actual results could differ.
Cost-Based Regulation	Cost-Based Regulation. The Duke Energy Registrants account for their regulated operations in accordance with applicable regulatory accounting guidance. The economic effects of regulation can result in a regulated company recording assets for costs that have been or are expected to be approved for recovery from customers in a future period or recording liabilities for amounts that are expected to be returned to customers in the rate-setting process in a period different from the period in which the amounts would be recorded by an unregulated enterprise. Accordingly, the Duke Energy Registrants record assets and liabilities that result from the regulated ratemaking process that would not be recorded under GAAP for nonregulated entities. Regulatory assets and liabilities are amortized consistent with the treatment of the related cost in the ratemaking process. Management continually assesses whether regulatory assets are probable of future recovery by considering factors such as applicable regulatory changes, recent rate orders applicable to other regulated entities and the status of any pending or potential deregulation legislation. Additionally, management continually assesses whether any regulatory liabilities have been incurred. Based on this continual assessment, management believes the existing regulatory assets are probable of recovery and that no regulatory liabilities, other than those recorded, have been incurred. These regulatory assets and liabilities are classified in the Consolidated Balance Sheets as Regulatory assets and Other in Current Assets and as Regulatory liabilities and Other in Current Liabilities, respectively. The Duke Energy Registrants periodically evaluate the applicability of regulatory accounting treatment by considering factors such as regulatory changes and the impact of competition. If cost-based regulation ends or competition increases, the Duke Energy Registrants may have to reduce their asset balances to reflect a market basis less than cost and write-off the associated regulatory assets and liabilities. If it becomes probable that part of the cost of a plant under construction or a recently completed plant will be disallowed for ratemaking purposes and a reasonable estimate of the amount of the disallowance can be made, that amount is recognized as a loss. In November 2011, in conjunction with the PUCO's approval of its new Electric Security Plan (ESP), Duke Energy Ohio ceased applying regulatory accounting treatment to generation operations within its Commercial Power segment. For further information, see Note 4.
Energy Purchases, Fuel Costs And Fuel Cost Deferrals	Energy Purchases, Fuel Costs and Fuel Cost Deferrals. The Duke Energy Registrants utilize cost-tracking mechanisms, commonly referred to as a fuel adjustment clause, to recover the retail portion of fuel and purchased power. The Duke Energy Registrants defer the related cost through Fuel used in electric generation and purchased power — regulated on the Consolidated Statement of Operations, unless a regulatory requirement exists for deferral through Operating Revenues. Fuel used in electric generation and purchased power — regulated includes fuel, purchased power and recoverable costs that are deferred through fuel clauses established by the Subsidiary Registrants' regulators. These clauses allow the Subsidiary Registrants to recover fuel costs, fuel-related costs and portions of purchased power costs through surcharges on customer rates. The Subsidiary Registrants record any under-recovery or over-recovery resulting from the differences between estimated and actual costs as a regulatory asset or regulatory liability until billed or refunded to customers, at which point the differences are adjusted through revenues. Indiana law limits the amount of fuel costs that Duke Energy Indiana can recover to an amount that will not result in earning a return in excess of that allowed by the IURC. As discussed in Note 4, beginning January 1, 2012, Duke Energy Ohio procures energy for its retail customers through a third-party auction. Purchases of energy through the auction process are a pass-through of costs for Duke Energy Ohio, with no affect on earnings. Subsequent to December 31, 2011, Duke Energy Ohio's generation assets are no longer dedicated to retail customers and, accordingly, Duke Energy Ohio can no longer recover their generation assets' energy purchases and fuel costs from regulated customers.
Cash and Cash Equivalents	Cash and Cash Equivalents. All highly liquid investments with maturities of three months or less at the date of acquisition are considered cash equivalents. At December 31, 2012, Duke Energy had cash and cash equivalents of $1,424 million, of which $731 million is held in foreign jurisdictions and is forecasted to be used to fund international operations and investments.
Restricted Cash	Restricted Cash. The Duke Energy Registrants have restricted cash related primarily to collateral assets, escrow deposits, and restricted cash of VIEs. Restricted cash balances are reflected in Other within Current Assets and in Other within Investments and Other Assets on the Consolidated Balance Sheets.
Inventory	Inventory. Inventory is comprised of amounts presented in the tables below and is recorded primarily using the average cost method. Inventory related to the Duke Energy Registrants' regulated operations is valued at historical cost consistent with ratemaking treatment. Materials and supplies are recorded as inventory when purchased and subsequently charged to expense or capitalized to property, plant and equipment when installed. Reserves are established for excess and obsolete inventory. Inventory related to the Duke Energy Registrants' nonregulated operations is valued at the lower of cost or market. The following tables present the Duke Energy Registrants' inventory. Duke Energy Ohio has agreements with a third party through which title of natural gas inventory purchased by Duke Energy Ohio is transferred to a third party. Under the agreements, the gas inventory is stored and managed for Duke Energy Ohio and is delivered on demand. As a result of the agreements, the combined natural gas inventory of approximately $44 million and $50 million being held by a third party as of December 31, 2012, and December 31, 2011, respectively, was classified as Other within Current Assets on the Consolidated Balance Sheets.
Investments In Debt And Equity Securities	Investments in Debt and Equity Securities. The Duke Energy Registrants classify investments into two categories — trading and available-for-sale. Trading securities are reported at fair value in the Consolidated Balance Sheets with net realized and unrealized gains and losses included in earnings each period. Available-for-sale securities are also reported at fair value on the Consolidated Balance Sheets with unrealized gains and losses included in Accumulated Other Comprehensive Income (AOCI) or as a regulatory asset or liability, unless it is determined that the carrying value of an investment is other-than-temporarily impaired. Other-than-temporary impairments related to equity securities and the credit loss portion of debt securities are included in earnings, unless deferred in accordance with regulatory accounting treatment. Investments in debt and equity securities are classified as either short-term investments or long-term investments based on management's intent and ability to sell these securities, taking into consideration illiquidity factors in the current markets with respect to certain investments that have historically provided for a high degree of liquidity, such as investments in auction rate debt securities. See Note 17 for further information on the investments in debt and equity securities, including investments held in the nuclear decommissioning trust funds (NDTF).
Goodwill	Goodwill. Duke Energy and Duke Energy Ohio perform annual goodwill impairment tests as of August 31 each year and update these tests between annual tests if events or circumstances occur that would more likely than not reduce the fair value of a reporting unit below its carrying value. In 2012, Progress Energy changed its goodwill impairment testing date from October 31 to August 31. The change in the goodwill impairment test date is preferable as it better aligns the annual goodwill impairment testing procedures with the testing procedures of Duke Energy. The change in accounting principle did not accelerate, delay, avoid, or cause a goodwill impairment charge. Neither the change in the goodwill impairment testing date nor the merger resulted in any changes to the Progress Energy reporting units. Due to significant judgments and estimates that are utilized in a goodwill impairment analysis, Progress Energy determined it was impracticable to objectively determine, without the use of hindsight, projected cash flows and related valuation estimates as of each August 31, for periods prior to August 31, 2012. As such, the change in the annual goodwill impairment testing date was prospectively applied from August 31, 2012. Duke Energy, Progress Energy and Duke Energy Ohio perform the annual review for goodwill impairment at the reporting unit level, which Duke Energy and Progress Energy have determined to be an operating segment or one level below and which Duke Energy Ohio has determined to be an operating segment. The annual goodwill impairment test may first consider qualitative factors to determine whether it is more likely than not (i.e. greater than 50 percent chance) that the fair value of a reporting unit is less than its book value. This is sometimes referred to as “step zero” and is an optional step in the annual goodwill impairment analysis (see further discussion as discussed in “New Accounting Standards” below). If the results of qualitative assessments indicate that the fair value of a reporting unit is more likely than not less than the carrying value of the reporting unit, the two-step impairment test is required. Step one of the impairment test involves comparing the fair values of reporting units with their carrying values, including goodwill. If the carrying amount is less than fair value in step one, further testing of goodwill is not performed. If the carrying amount of a reporting unit exceeds the reporting unit's fair value, step two must be performed to determine the amount, if any, of the goodwill impairment loss. Step two of the goodwill impairment test involves comparing the implied fair value of the reporting unit's goodwill against the carrying value of the goodwill. Under step two, determining the implied fair value of goodwill requires the valuation of a reporting unit's identifiable tangible and intangible assets and liabilities as if the reporting unit had been acquired in a business combination on the testing date. The difference between the fair value of the entire reporting unit as determined in step one and the net fair value of all identifiable assets and liabilities represents the implied fair value of goodwill. The goodwill impairment charge, if any, would be the excess of the carrying amount of goodwill over the implied fair value of goodwill upon the completion of step two. As a result of the Progress Energy merger, Duke Energy, Progress Energy and Duke Energy Ohio performed step one of the goodwill impairment test as of August 31, 2012, and concluded the fair value of the reporting units exceeded their respective carrying values, and thus, did not record any impairment charges. In 2011, Duke Energy and Duke Energy Ohio performed the qualitative assessments under step zero and concluded that it was more likely than not the fair value of each reporting unit exceeded its carrying value. In 2011, Progress Energy performed step one of the goodwill impairment test, which indicated the carrying amounts of goodwill were not impaired. In 2010, Duke Energy, Progress Energy and Duke Energy Ohio used the two-step process to test goodwill for impairment, which resulted in impairments recorded by Duke Energy and Duke Energy Ohio. See Note 12 for further information.
Long-Lived Asset Impairments	Long-Lived Asset Impairments. The Duke Energy Registrants evaluate whether long-lived assets, excluding goodwill, have been impaired when circumstances indicate the carrying value of those assets may not be recoverable. For such long-lived assets, an impairment exists when its carrying value exceeds the sum of estimates of the undiscounted cash flows expected to result from the use and eventual disposition of the asset. When alternative courses of action to recover the carrying amount of a long-lived asset are under consideration, a probability-weighted approach is used for developing estimates of future undiscounted cash flows. If the carrying value of the long-lived asset is not recoverable based on these estimated future undiscounted cash flows, the impairment loss is measured as the excess of the carrying value of the asset over its fair value, such that the asset's carrying value is adjusted to its estimated fair value. Management assesses the fair value of long-lived assets using commonly accepted techniques, and may use more than one source. Sources to determine fair value include, but are not limited to, recent third party comparable sales, internally developed discounted cash flow analysis and analysis from outside advisors. Significant changes in market conditions resulting from events such as, among others, changes in commodity prices or the condition of an asset, or a change in management's intent to utilize the asset are generally viewed by management as triggering events to re-assess the cash flows related to the long-lived assets. See Note 12 for further information.
Property, Plant and Equipment	Property, Plant and Equipment. Property, plant and equipment are stated at the lower of historical cost less accumulated depreciation or fair value, if impaired. The Duke Energy Registrants capitalize all construction-related direct labor and material costs, as well as indirect construction costs. Indirect costs include general engineering, taxes and the allowance for funds used during construction (AFUDC). See “AFUDC and Interest Capitalized,” below for additional information. The cost of renewals and betterments that extend the useful life of property, plant and equipment are also capitalized. The cost of repairs, replacements and major maintenance projects, which do not extend the useful life or increase the expected output of the asset, are expensed as incurred. Depreciation is generally computed over the estimated useful life of the asset using the composite straight-line method. For regulated operations, depreciation studies are conducted periodically to update the composite rates and are approved by the various state commissions. The composite weighted-average depreciation rates, excluding nuclear fuel, for each of the Duke Energy Registrants are included in the following table: When the Duke Energy Registrants retire regulated property, plant and equipment under what is considered a normal retirement, the original cost plus the cost of retirement, less salvage value, is charged to accumulated depreciation, consistent with regulated rate-making practices. When it becomes probable that a regulated generation asset will be retired substantially in advance of its original expected useful life or is abandoned, the cost of the asset and the corresponding accumulated depreciation is removed from Cost and Accumulated depreciation and amortization within Property, Plant and Equipment on the Consolidated Balance Sheets and a separate asset is recognized. If the plant is still in operation, the amount is classified as Generation facilities to be retired, net on the Consolidated Balance Sheets. If the plant is no longer operating, then a regulatory asset is recognized. The carrying value of the asset is based on historical cost if the Duke Energy Registrants are allowed to recover the remaining net book value and a full return on the asset. If the Duke Energy Registrants do not expect to recover the full remaining cost and a full return, the carrying value of the asset is based on the lower of cost or the present value of the future revenues expected to be provided to recover the allowable costs discounted at the Duke Energy Registrants' incremental borrowing rate. An impairment is recognized if the net book value of the asset exceeds the present value of the future revenues to be recovered in rates. When the Duke Energy Registrants sell entire regulated operating units, or retire or sell nonregulated properties, the original cost is removed from property and the related accumulated depreciation and amortization balances are reduced. Any gain or loss is recorded in earnings, unless otherwise required by the applicable regulatory body. See Note 10 for further information on the components and estimated useful lives of Duke Energy's property, plant and equipment.
Nuclear Fuel	Nuclear Fuel. Nuclear fuel is classified as Property, Plant and Equipment in the Consolidated Balance Sheets. Nuclear fuel in the front-end fuel processing phase is considered work in progress and not amortized until placed in service. Amortization of nuclear fuel is included within Fuel used in electric generation and purchased power-regulated in the Consolidated Statements of Operations. The amortization is recorded using the units-of-production method.
AFUDC And Interest Capitalized	AFUDC and Interest Capitalized. In accordance with applicable regulatory accounting guidance, the Duke Energy Registrants record AFUDC, which represents the estimated debt and equity costs of capital funds necessary to finance the construction of new regulated facilities. The equity component of AFUDC is a non-cash amount within the Consolidated Statements of Operations. AFUDC is capitalized as a component of the cost of property, plant and equipment, with an offsetting credit to Other income and expenses, net on the Consolidated Statements of Operations for the equity component and as an offset to Interest Expense on the Consolidated Statements of Operations for the debt component. After construction is completed, the Duke Energy Registrants are permitted to recover these costs through inclusion in the rate base and the corresponding depreciation expense or nuclear fuel expense. AFUDC equity is a permanent difference item for income tax purposes, thus reducing the Duke Energy Registrants' effective tax rate during the construction phase in which AFUDC equity is being recorded. The effective tax rate is subsequently increased in future periods when the completed property, plant and equipment are placed in service and depreciation of the AFUDC equity commences. See Note 24 for information related to the impacts of AFUDC equity on the Duke Energy Registrants' effective tax rate. For nonregulated operations, interest is capitalized during the construction phase in accordance with the applicable accounting guidance.
Asset Retirement Obligations	Asset Retirement Obligations. The Duke Energy Registrants recognize asset retirement obligations for legal obligations associated with the retirement of long-lived assets that result from the acquisition, construction, development and/or normal use of the asset, and for conditional asset retirement obligations. The term conditional asset retirement obligation refers to a legal obligation to perform an asset retirement activity in which the timing and (or) method of settlement are conditional on a future event that may or may not be within the control of the entity. The obligation to perform the asset retirement activity is unconditional even though uncertainty exists about the timing and (or) method of settlement. Thus, the timing and (or) method of settlement may be conditional on a future event. When recording an asset retirement obligation, the present value of the projected liability is recognized in the period in which it is incurred, if a reasonable estimate of fair value can be made. The liability is then accreted over time by applying an interest method of allocation to the liability. Substantially all accretion is related to regulated operations and is deferred pursuant to regulatory accounting. The present value of the liability is added to the carrying amount of the associated asset and this additional carrying amount is depreciated over the remaining life of the asset. The present value of the initial obligation and subsequent updates are based on discounted cash flows, which include estimates regarding the timing of future cash flows, the selection of discount rates and cost escalation rates, among other factors. These underlying assumptions and estimates are made as of a point in time and are subject to change. The obligations for nuclear decommissioning are based on site-specific cost studies. Duke Energy Carolinas and Progress Energy Carolinas assume prompt dismantlement of the nuclear facilities, which reflects dismantling the site after operations are ceased. Progress Energy Florida assumes the nuclear facility will be placed into a safe storage configuration until the eventual dismantling of the site begins in approximately 40-60 years. The nuclear decommissioning asset retirement obligation also assumes Duke Energy Carolinas, Progress Energy Carolinas and Progress Energy Florida will store spent fuel on site until such time that it can be transferred to a U.S. Department of Energy (DOE) facility. See Note 9 for further information.
Unbilled Revenue	Revenue Recognition and Unbilled Revenue. Revenues on sales of electricity and gas are recognized when either the service is provided or the product is delivered. Unbilled retail revenues are estimated by applying average revenue per kilowatt-hour (kWh) or per thousand cubic feet (Mcf) for all customer classes to the number of estimated kWh or Mcf delivered but not billed. Unbilled wholesale energy revenues are calculated by applying the contractual rate per megawatt-hour (MWh) to the number of estimated MWh delivered but not yet billed. Unbilled wholesale demand revenues are calculated by applying the contractual rate per megawatt (MW) to the MW volume delivered but not yet billed. The amount of unbilled revenues can vary significantly from period to period as a result of numerous factors, including seasonality, weather, customer usage patterns and customer mix. The Duke Energy Registrants had unbilled revenues within Receivables and within Restricted receivables of variable interest entities on their respective Consolidated Balance Sheets as shown in the table below. Additionally, Duke Energy Ohio and Duke Energy Indiana sell, on a revolving basis, nearly all of their retail and wholesale accounts receivable to Cinergy Receivables Company, LLC (CRC). These transfers meet sales/derecognition criteria and, therefore, Duke Energy Ohio and Duke Energy Indiana account for the transfers of receivables to Cinergy Receivables as sales. Accordingly, the receivables sold are not reflected on the Consolidated Balance Sheets of Duke Energy Ohio and Duke Energy Indiana. See Note 18 for further information. Receivables for unbilled revenues related to retail and wholesale accounts receivable at Duke Energy Ohio and Duke Energy Indiana included in the sales of accounts receivable to CRC were as shown in the table below.
Accounting For Risk Management, Hedging Activities And Financial Instruments	Accounting for Risk Management, Hedging Activities and Financial Instruments. The Duke Energy Registrants may use a number of different derivative and non-derivative instruments in connection with their commodity price, interest rate and foreign currency risk management activities, including swaps, futures, forwards and options. All derivative instruments except those that qualify for the normal purchase/normal sale (NPNS) exception within the accounting guidance for derivatives are recorded on the Consolidated Balance Sheets at their fair value. The effective portion of the change in the fair value of derivative instruments designated as cash flow hedges is recorded in AOCI. The effective portion of the change in the fair value of a fair value hedge is offset in net income by changes in the hedged item. The Duke Energy Registrants may designate qualifying derivative instruments as either cash flow hedges or fair value hedges, while others either have not been designated as hedges or do not qualify as a hedge (hereinafter referred to as undesignated contracts). For all contracts accounted for as a hedge, the Duke Energy Registrants prepare formal documentation of the hedge in accordance with the accounting guidance for derivatives. In addition, at inception and at least every three months thereafter, the Duke Energy Registrants formally assess whether the hedge contract is highly effective in offsetting changes in cash flows or fair values of hedged items. The Duke Energy Registrants document hedging activity by transaction type and risk management strategy. See Note 15 for further information.
Captive Insurance Reserves	Captive Insurance Reserves. Duke Energy has captive insurance subsidiaries that provide coverage, on an indemnity basis, to the Subsidiary Registrants as well as certain third parties, on a limited basis, for various business risks and losses, such as property, business interruption, workers' compensation and general liability. Liabilities include provisions for estimated losses incurred but not yet reported (IBNR), as well as provisions for known claims which have been estimated on a claims-incurred basis. IBNR reserve estimates involve the use of assumptions and are primarily based upon historical loss experience, industry data and other actuarial assumptions. Reserve estimates are adjusted in future periods as actual losses differ from historical experience. Duke Energy, through its captive insurance entities, also has reinsurance coverage with third parties, which provides reimbursement for certain losses above a per occurrence and/or aggregate retention. Duke Energy recognizes a reinsurance receivable for recovery of incurred losses under its captive's reinsurance coverage once realization of the receivable is deemed probable.
Unamortized Debt Premium, Discount And Expense	Unamortized Debt Premium, Discount and Expense. Premiums, discounts and expenses incurred with the issuance of outstanding long-term debt are amortized over the terms of the debt issues. Any call premiums or unamortized expenses associated with refinancing higher-cost debt obligations used to finance regulated assets and operations are amortized consistent with regulatory treatment of those items, where appropriate. The amortization expense is recorded as a component of Interest Expense in the Consolidated Statements of Operations and is reflected as Depreciation, amortization and accretion within Net cash provided by operating activities on the Consolidated Statements of Cash Flows.
Loss Contingencies And Environmental Liabilities	Loss Contingencies and Environmental Liabilities. The Duke Energy Registrants are involved in certain legal and environmental matters that arise in the normal course of business. Contingent losses are recorded when it is determined that it is probable that a loss has occurred and the amount of the loss can be reasonably estimated. When a range of the probable loss exists and no amount within the range is a better estimate than any other amount, the Duke Energy Registrants record a loss contingency at the minimum amount in the range. Unless otherwise required by GAAP, legal fees are expensed as incurred. Environmental liabilities are recorded on an undiscounted basis when the necessity for environmental remediation becomes probable and the costs can be reasonably estimated, or when other potential environmental liabilities are reasonably estimable and probable. The Duke Energy Registrants expense environmental expenditures related to conditions caused by past operations that do not generate current or future revenues. Certain environmental expenses receive regulatory accounting treatment, under which the expenses are recorded as regulatory assets. Environmental expenditures related to operations that generate current or future revenues are expensed or capitalized, as appropriate. See Note 5 for further information.
Pension And Other Post-Retirement Benefit Plans	Pension and Other Post-Retirement Benefit Plans. Duke Energy maintains qualified, non-qualified and other post-retirement benefit plans. Eligible employees of the Subsidiary Registrants participate in the respective Duke Energy or Progress Energy qualified, non-qualified and other post-retirement benefit plans and are allocated their proportionate share of benefit costs. See Note 23 for information related to Duke Energy's benefit plans, including certain accounting policies associated with these plans.
Severance And Special Termination Benefits	Severance and Special Termination Benefits. Duke Energy has an ongoing severance plan under which, in general, the longer a terminated employee worked prior to termination the greater the amount of severance benefits. The Duke Energy Registrants record a liability for involuntary severance once an involuntary severance plan is committed to by management, or sooner, if involuntary severances are probable and the related severance benefits can be reasonably estimated. For involuntary severance benefits that are incremental to its ongoing severance plan benefits, Duke Energy measures the obligation and records the expense at its fair value at the communication date if there are no future service requirements, or, if future service is required to receive the termination benefit, ratably over the service period. From time to time, Duke Energy offers special termination benefits under voluntary severance programs. Special termination benefits are measured upon employee acceptance and recorded immediately absent a significant retention period. If a significant retention period exists, the cost of the special termination benefits are recorded ratably over the remaining service periods of the affected employees. Employee acceptance of voluntary severance benefits is determined by management based on the facts and circumstances of the special termination benefits being offered. See Note 21 for further information.
Guarantees	Guarantees. Upon issuance or modification of a guarantee, the Duke Energy Registrants recognize a liability at the time of issuance or material modification for the estimated fair value of the obligation it assumes under that guarantee, if any. Fair value is estimated using a probability-weighted approach. The Duke Energy Registrants reduce the obligation over the term of the guarantee or related contract in a systematic and rational method as risk is reduced under the obligation. Any additional contingent loss for guarantee contracts subsequent to the initial recognition of a liability in accordance with applicable accounting guidance is accounted for and recognized at the time a loss is probable and the amount of the loss can be reasonably estimated. The Duke Energy Registrants have entered into various indemnification agreements related to purchase and sale agreements and other types of contractual agreements with vendors and other third parties. These agreements typically cover environmental, tax, litigation and other matters, as well as breaches of representations, warranties and covenants. Typically, claims may be made by third parties for various periods of time, depending on the nature of the claim. Potential exposure under these indemnification agreements can range from a specified to an unlimited dollar amount, depending on the nature of the claim and the particular transaction. See Note 7 for further information.
Stock-based Compensation	Stock-Based Compensation. Stock-based compensation represents the cost related to stock-based awards granted to employees. Duke Energy recognizes stock-based compensation based upon the estimated fair value of the awards, net of estimated forfeitures. The recognition period for these costs begin at either the applicable service inception date or grant date and continues throughout the requisite service period, or for certain share-based awards until the employee becomes retirement eligible, if earlier. Share-based awards, including stock options, but not performance shares, granted to employees that are already retirement eligible are deemed to have vested immediately upon issuance, and, therefore, compensation cost for those awards is recognized on the date such awards are granted. See Note 22 for further information.
Accounting For Purchases And Sales Of Emission Allowances	Accounting For Purchases and Sales of Emission Allowances. Emission allowances are issued by the Environmental Protection Agency (EPA) at zero cost and permit the holder of the allowance to emit certain gaseous by-products of fossil fuel combustion, including sulfur dioxide (SO2) and nitrogen oxide (NOx). Allowances may also be bought and sold via third-party transactions. Allowances allocated to or acquired by the Duke Energy Registrants are held primarily for consumption. Emission allowances at cost are included in Intangibles, net on the Consolidated Balance Sheets and the Duke Energy Registrants recognize expense as the allowances are consumed or sold. Gains or losses on sales of emission allowances by regulated businesses that do not provide for direct recovery through a cost-tracking mechanism and by nonregulated businesses are presented in Gains on Sales of Other Assets and Other, net, in the Consolidated Statements of Operations. For regulated businesses that provide for direct recovery of emission allowances, any gain or loss on sales of recoverable emission allowances are included in the rate structure of the regulated entity and are deferred as a regulatory asset or liability. Future rates charged to retail customers are impacted by any gain or loss on sales of recoverable emission allowances. Purchases and sales of emission allowances are presented gross as investing activities on the Consolidated Statements of Cash Flows. See Note 12 for discussion regarding the impairment of the carrying value of certain emission allowances in 2011.
Income Taxes	Income Taxes. Duke Energy and its subsidiaries file a consolidated federal income tax return and other state and foreign jurisdictional returns as required. Deferred income taxes have been provided for temporary differences between the GAAP and tax carrying amounts of assets and liabilities. These differences create taxable or tax-deductible amounts for future periods. Investment tax credits (ITC) associated with regulated operations are deferred and are amortized as a reduction of income tax expense over the estimated useful lives of the related properties. The Subsidiary Registrants entered into a tax sharing agreement with Duke Energy, where the separate return method is used to allocate tax expenses and benefits to the subsidiaries whose investments or results of operations provide these tax expenses or benefits. The accounting for income taxes essentially represents the income taxes that the Subsidiary Registrants would incur if the Subsidiary Registrants were a separate company filing its own federal tax return as a C-Corporation. The Duke Energy Registrants record unrecognized tax benefits for positions taken or expected to be taken on tax returns, including the decision to exclude certain income or transactions from a return, when a more-likely-than-not threshold is met for a tax position and management believes that the position will be sustained upon examination by the taxing authorities. Management evaluates each position based solely on the technical merits and facts and circumstances of the position, assuming the position will be examined by a taxing authority having full knowledge of all relevant information. The Duke Energy Registrants record the largest amount of the unrecognized tax benefit that is greater than 50% likely of being realized upon settlement or effective settlement. Management considers a tax position effectively settled for the purpose of recognizing previously unrecognized tax benefits when the following conditions exist: (i) the taxing authority has completed its examination procedures, including all appeals and administrative reviews that the taxing authority is required and expected to perform for the tax positions, (ii) the Duke Energy Registrants do not intend to appeal or litigate any aspect of the tax position included in the completed examination, and (iii) it is remote that the taxing authority would examine or reexamine any aspect of the tax position. Deferred taxes are not provided on translation gains and losses where Duke Energy expects earnings of a foreign operation to be indefinitely reinvested. The Duke Energy Registrants record tax-related interest expense in Interest Expense and interest income and penalties in Other Income and Expenses, net, in the Consolidated Statements of Operations. See Note 24 for further information.
Accounting For Renewable Energy Tax Credits And Grants Under the American Recovery Act of 2009	Accounting for Renewable Energy Tax Credits and Grants. In 2009, The American Recovery and Reinvestment Act of 2009 (the Stimulus Bill) was signed into law, which provides tax incentives in the form of ITC or cash grants for renewable energy facilities and renewable generation property either placed in service through specified dates or for which construction has begun prior to specified dates. Under the Stimulus Bill, Duke Energy may elect an ITC, which is determined based on a percentage of the tax basis of the qualified property placed in service, for property placed in service after 2008 and before 2014 (2013 for wind facilities) or a cash grant, which allows entities to elect to receive a cash grant in lieu of the ITC for certain property either placed in service in 2009 or 2010 or for which construction begins in 2009 and 2010. In 2010, the Tax Relief, Unemployment Insurance Reauthorization, and Job Creation Act of 2010 (the 2010 Tax Relief Act) extended the cash grant program for renewable energy property for one additional year, through 2011. In 2011, the Budget Control Act of 2011 (BCA) was passed which provided for an automatic reduction in defense and non-defense spending beginning January 1, 2013, which could reduce future cash grant payments since such grants are likely to be treated as non-defense discretionary spending subject to reduction under the sequester. In 2012, the American Taxpayer Relief Act of 2012 (the ATRA) extended the ITC (energy credit) and production tax credits available for wind facilities one year, through 2013, and changed the timing for determining property eligible for the ITC, from property placed in service before the credit deadline, to property under construction by the applicable deadline for the credit. The ATRA delayed the start of the automatic reductions/sequester under the BCA from January 1 to March 1, 2013. When Duke Energy elects either the ITC or cash grant on Commercial Power's wind or solar facilities that meet the stipulations of the Stimulus Bill, Duke Energy reduces the basis of the property recorded on the Consolidated Balance Sheets by the amount of the ITC or cash grant and, therefore, the ITC or grant benefit is recognized ratably over the life of the associated asset through reduced depreciation expense. Additionally, certain tax credits and government grants received under the Stimulus Bill provide for an incremental initial tax depreciable base in excess of the carrying value for GAAP purposes, creating an initial deferred tax asset equal to the tax effect of one half of the ITC or government grant. Duke Energy records the deferred tax benefit as a reduction to income tax expense in the period that the basis difference is created.
Excise Taxes	Excise Taxes. Certain excise taxes levied by state or local governments are collected by the Duke Energy Registrants from their customers. These taxes, which are required to be paid regardless of the Duke Energy Registrants' ability to collect from the customer, are accounted for on a gross basis. When the Duke Energy Registrants act as an agent, and the tax is not required to be remitted if it is not collected from the customer, the taxes are accounted for on a net basis. The Duke Energy Registrants' excise taxes accounted for on a gross basis and recorded as operating revenues in the Consolidated Statements of Operations were as follows:
Foreign Currency Transaction	Foreign Currency Translation. The local currencies of Duke Energy's foreign operations have been determined to be their functional currencies, except for certain foreign operations whose functional currency has been determined to be the U.S. Dollar, based on an assessment of the economic circumstances of the foreign operation. Assets and liabilities of foreign operations, except for those whose functional currency is the U.S. Dollar, are translated into U.S. Dollars at the exchange rates in effect at period end. Translation adjustments resulting from fluctuations in exchange rates are included as a separate component of AOCI. Revenue and expense accounts of these operations are translated at average exchange rates prevailing during the year. Gains and losses arising from balances and transactions denominated in currencies other than the functional currency are included in the results of operations in the period in which they occur.
Dividend Restrictions And Unappropriated Retained Earnings	Dividend Restrictions and Unappropriated Retained Earnings. Duke Energy does not have any legal, regulatory or other restrictions on paying common stock dividends to shareholders. However, as further described in Note 4, due to conditions established by regulators at the time of the Duke Energy/Cinergy merger in April 2006 and the Duke Energy/Progress Energy merger in 2012, certain wholly owned subsidiaries, including Duke Energy Carolinas, Progress Energy Carolinas, Duke Energy Ohio and Duke Energy Indiana, have restrictions on paying dividends or otherwise advancing funds to Duke Energy. At December 31, 2012 and 2011, an insignificant amount of Duke Energy's consolidated Retained earnings balance represents undistributed earnings of equity method investments.
New Accounting Standards [Policy Text Block]	New Accounting Standards. The following new accounting standards were adopted by the Duke Energy Registrants during the year ended December 31, 2012, and the impact of such adoption, if applicable, has been presented in the accompanying Consolidated Financial Statements: Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC) 220 — Comprehensive Income. In June 2011, the FASB amended the existing requirements for presenting comprehensive income in financial statements primarily to increase the prominence of items reported in other comprehensive income (OCI) and to facilitate the convergence of U.S. GAAP and International Financial Reporting Standards (IFRS). Specifically, the revised guidance eliminates the option previously provided to present components of OCI as part of the statement of changes in stockholders' equity. Accordingly, all non-owner changes in stockholders' equity are required to be presented either in a single continuous statement of comprehensive income or in two separate but consecutive financial statements. For the Duke Energy Registrants, this revised guidance was effective on a retrospective basis for interim and annual periods beginning January 1, 2012. The adoption of this standard changed the presentation of the Duke Energy Registrants' financial statements but did not affect the calculation of net income, comprehensive income or earnings per share. ASC 820 — Fair Value Measurements and Disclosures. In May 2011, the FASB amended existing requirements for measuring fair value and for disclosing information about fair value measurements. This revised guidance results in a consistent definition of fair value, as well as common requirements for measurement and disclosure of fair value information between U.S. GAAP and IFRS. In addition, the amendments set forth enhanced disclosure requirements with respect to recurring Level 3 measurements, nonfinancial assets measured or disclosed at fair value, transfers between levels in the fair value hierarchy, and assets and liabilities disclosed but not recorded at fair value. For the Duke Energy Registrants, the revised fair value measurement guidance was effective on a prospective basis for interim and annual periods beginning January 1, 2012. The adoption of this new guidance did not have a significant impact on the Duke Energy Registrants disclosures or their consolidated results of operations, cash flows, or financial position. The following new accounting standards were adopted by Duke Energy during the year ended December 31, 2011, and the impact of such adoption, if applicable has been presented in the accompanying Consolidated Financial Statements: ASC 605 — Revenue Recognition. In October 2009, the FASB issued new revenue recognition accounting guidance in response to practice concerns related to the accounting for revenue arrangements with multiple deliverables. This new accounting guidance primarily applies to all contractual arrangements in which a vendor will perform multiple revenue generating activities and addresses the unit of accounting for arrangements involving multiple deliverables, as well as how arrangement consideration should be allocated to the separate units of accounting. For the Duke Energy Registrants, the new accounting guidance was effective January 1, 2011, and applied on a prospective basis. This new accounting guidance did not have a material impact to the consolidated results of operations, cash flows or financial position of the Duke Energy Registrants. ASC 805 — Business Combinations. In November 2010, the FASB issued new accounting guidance in response to diversity in the interpretation of pro forma information disclosure requirements for business combinations. The new accounting guidance requires an entity to present pro forma financial information as if a business combination occurred at the beginning of the earliest period presented as well as additional disclosures describing the nature and amount of material, nonrecurring pro forma adjustments. This new accounting guidance was effective January 1, 2011, and has been applied to all business combinations consummated after that date. ASC 820 — Fair Value Measurements and Disclosures. In January 2010, the FASB amended existing fair value measurements and disclosures accounting guidance to clarify certain existing disclosure requirements and to require a number of additional disclosures, including amounts and reasons for significant transfers between the three levels of the fair value hierarchy, and presentation of certain information in the reconciliation of recurring Level 3 measurements on a gross basis. For the Duke Energy Registrants, certain portions of this revised accounting guidance were effective on January 1, 2010, with additional disclosures effective for periods beginning January 1, 2011. The adoption of this accounting guidance resulted in additional disclosure in the notes to the consolidated financial statements but did not have an impact on the Duke Energy Registrants' consolidated results of operations, cash flows or financial position. ASC 350 — Intangibles–Goodwill and Other. In September 2011, the FASB amended existing goodwill impairment testing accounting guidance to provide an entity testing goodwill for impairment with the option of performing a qualitative assessment prior to calculating the fair value of a reporting unit in step one of a goodwill impairment test. Under this revised guidance, a qualitative assessment would require an evaluation of economic, industry, and company-specific considerations. If an entity determines, on a basis of such qualitative factors, that the fair value of a reporting unit is more likely than not less than the carrying value of a reporting unit, the two-step impairment test, as required under pre-existing applicable accounting guidance, would be required. Otherwise, no further impairment testing would be required. The revised goodwill impairment testing accounting guidance is effective for the Duke Energy Registrants' annual and interim goodwill impairment tests performed for fiscal years beginning January 1, 2012, with early adoption of this revised guidance permitted for annual and interim goodwill impairment tests performed as of a date before September 15, 2011. Since annual goodwill impairment tests are performed by Duke Energy as of August 31, the Duke Energy Registrants early adopted this revised accounting guidance during the third quarter of 2011 and applied that guidance to their annual goodwill impairment tests for 2011. The following new accounting standards were adopted by Duke Energy during the year ended December 31, 2010, and the impact of such adoption, if applicable has been presented in the accompanying Consolidated Financial Statements: ASC 860 — Transfers and Servicing. In June 2009, the FASB issued revised accounting guidance for transfers and servicing of financial assets and extinguishment of liabilities, to require additional information about transfers of financial assets, including securitization transactions, as well as additional information about an enterprise's continuing exposure to the risks related to transferred financial assets. This revised accounting guidance eliminated the concept of a Qualifying Special Purpose Entity (QSPE) and required those entities which were not subject to consolidation under previous accounting rules to now be assessed for consolidation. In addition, this accounting guidance clarified and amended the derecognition criteria for transfers of financial assets (including transfers of portions of financial assets) and required additional disclosures about a transferor's continuing involvement in transferred financial assets. For Duke Energy, this revised accounting guidance was effective prospectively for transfers of financial assets occurring on or after January 1, 2010, and early adoption of this statement was prohibited. Since 2002, Duke Energy Ohio, Duke Energy Indiana, and Duke Energy Kentucky have sold, on a revolving basis, nearly all of their accounts receivable and related collections through CRC, a bankruptcy-remote QSPE. The securitization transaction was structured to meet the criteria for sale accounting treatment, and, accordingly, Duke Energy did not consolidate CRC, and the transfers were accounted for as sales. Effective with adoption of this revised accounting guidance and ASC 810-Consolidation, as discussed below, the accounting treatment and/or financial statement presentation of Duke Energy's accounts receivable securitization programs was impacted as Duke Energy began consolidating CRC effective January 1, 2010. Duke Energy Ohio's and Duke Energy Indiana's sales of accounts receivable and related financial statement presentation were not impacted by the adoption of ASC 860. ASC 810 — Consolidations. In June 2009, the FASB amended existing consolidation accounting guidance to eliminate the exemption from consolidation for QSPEs, and clarified, but did not significantly change, the criteria for determining whether an entity meets the definition of a VIE. This revised accounting guidance also required an enterprise to qualitatively assess the determination of the primary beneficiary of a VIE based on whether that enterprise has both the power to direct the activities that most significantly impact the economic performance of a VIE and the obligation to absorb losses or the right to receive benefits of a VIE that could potentially be significant to a VIE. In addition, this revised accounting guidance modified existing accounting guidance to require an ongoing evaluation of a VIE's primary beneficiary and amended the types of events that trigger a reassessment of whether an entity is a VIE. Furthermore, this accounting guidance required enterprises to provide additional disclosures about their involvement with VIEs and any significant changes in their risk exposure due to that involvement. For the Duke Energy Registrants, this accounting guidance was effective beginning on January 1, 2010, and is applicable to all entities in which Duke Energy is involved, including entities previously subject to existing accounting guidance for VIEs, as well as any QSPEs that existed as of the effective date. Effective with adoption of this revised accounting guidance, the accounting treatment and/or financial statement presentation of Duke Energy's accounts receivable securitization programs were impacted as Duke Energy began consolidating CRC effective January 1, 2010. Duke Energy Ohio's and Duke Energy Indiana's sales of accounts receivable and related financial statement presentation were not impacted by the adoption of ASC 810. This revised accounting guidance did not have a significant impact on any of the Duke Energy Registrants' other interests in VIEs. ASC 820 — Fair Value Measurements and Disclosures. In January 2010, the FASB amended existing fair value measurements and disclosures accounting guidance to clarify certain existing disclosure requirements and to require a number of additional disclosures, including amounts and reasons for significant transfers between the three levels of the fair value hierarchy, and presentation of certain information in the reconciliation of recurring Level 3 measurements on a gross basis. For the Duke Energy Registrants, certain portions of this revised accounting guidance were effective on January 1, 2010, with additional disclosures effective for periods beginning January 1, 2011. The initial adoption of this accounting guidance resulted in additional disclosure in the notes to the consolidated financial statements but did not have an impact on the Duke Energy Registrants' consolidated results of operations, cash flows or financial position. The following new Accounting Standards Updates (ASU) have been issued, but have not yet been adopted by Duke Energy, as of December 31, 2012. ASC 210 — Balance Sheet. In December 2011, the FASB issued revised accounting guidance to amend the existing disclosure requirements for offsetting financial assets and liabilities to enhance current disclosures, as well as to improve comparability of balance sheets prepared under U.S. GAAP and IFRS. The revised disclosure guidance affects all companies that have financial instruments and derivative instruments that are either offset in the balance sheet (i.e., presented on a net basis) or subject to an enforceable master netting arrangement and/or similar agreement. The revised guidance requires that certain enhanced quantitative and qualitative disclosures be made with respect to a company's netting arrangements and/or rights of setoff associated with its financial instruments and/or derivative instruments including associated collateral. For the Duke Energy Registrants, the revised disclosure guidance is effective on a retrospective basis for interim and annual periods beginning January 1, 2013. Other than additional disclosures, this revised guidance does not impact the Duke Energy Registrants' consolidated results of operations, cash flows or financial position. ASC 220 — Comprehensive Income. In February 2013, the FASB amended the existing requirements for presenting comprehensive income in financial statements to improve the reporting of reclassifications out of AOCI. The amendments in this Update seek to attain that objective by requiring an entity to report the effect of significant reclassifications out of AOCI on the respective line items in net income if the amount being reclassified is required under U.S. GAAP to be reclassified in its entirety to net income. For other amounts that are not required under U.S. GAAP to be reclassified in their entirety to net income in the same reporting period, an entity is required to cross-reference other disclosures required under U.S. GAAP that provide additional detail about those amounts. This would be the case when a portion of the amount reclassified out of AOCI is reclassified to a balance sheet account (for example, inventory) instead of directly to income or expense in the same reporting period. For the Duke Energy Registrants, this revised guidance is effective on a prospective basis for interim and annual periods beginning January 1, 2013. Other than additional disclosures or a change in the presentation on the statement of comprehensive income, this revised guidance does not impact the Duke Energy Registrants' consolidated results of operations, cash flows or financial position.
Duke Energy Carolinas [Member]
Policy Text Block [Line Items]
Organization	Nature of Operations and Basis of Consolidation. Duke Energy Corporation (collectively with its subsidiaries, Duke Energy), is an energy company headquartered in Charlotte, North Carolina. Duke Energy operates in the United States (U.S.) and Latin America primarily through its direct and indirect subsidiaries. Duke Energy's subsidiaries included Duke Energy Carolinas, LLC (Duke Energy Carolinas), Duke Energy Ohio, Inc. (Duke Energy Ohio), which includes Duke Energy Kentucky, Inc. (Duke Energy Kentucky), and Duke Energy Indiana, Inc. (Duke Energy Indiana) prior to the merger with Progress Energy, Inc. (Progress Energy). On July 2, 2012, Duke Energy merged with Progress Energy, with Duke Energy continuing as the surviving corporation, and Progress Energy becoming a subsidiary of Duke Energy. Carolina Power & Light Company d/b/a Progress Energy Carolinas, Inc. (Progress Energy Carolinas) and Florida Power Corporation d/b/a Progress Energy Florida, Inc. (Progress Energy Florida), Progress Energy's regulated utility subsidiaries, are now indirect subsidiaries of Duke Energy. Duke Energy's consolidated financial statements include Progress Energy, Progress Energy Carolinas and Progress Energy Florida activity beginning July 2, 2012. See Note 2 for additional information regarding the merger. When discussing Duke Energy's consolidated financial information, it necessarily includes the results of its six separate subsidiary registrants, Duke Energy Carolinas, Progress Energy, Progress Energy Carolinas, Progress Energy Florida, Duke Energy Ohio and Duke Energy Indiana (collectively referred to as the Subsidiary Registrants), which, along with Duke Energy, are collectively referred to as the Duke Energy Registrants. Progress Energy, Progress Energy Carolinas and Progress Energy Florida (collectively referred to as the Progress Energy Registrants) continue to maintain reporting requirements as SEC registrants. In accordance with SEC guidance, the Progress Energy Registrants did not reflect the impacts of acquisition accounting from the merger with Duke Energy, whereby the adjustments of assets and liabilities to fair value and the resultant goodwill would be shown on the financial statements of the Progress Energy Registrants. These adjustments were recorded by Duke Energy. The information in these combined notes relates to each of the Duke Energy Registrants as noted in the Index to the Combined Notes. However, none of the registrants makes any representation as to information related solely to Duke Energy or the subsidiaries of Duke Energy other than itself. As discussed further in Note 3, Duke Energy operates three reportable business segments: U.S. Franchised Electric and Gas (USFE&G), Commercial Power and International Energy. The remainder of Duke Energy's operations is presented as Other. These Consolidated Financial Statements include, after eliminating intercompany transactions and balances, the accounts of the Duke Energy Registrants and all majority-owned subsidiaries where the respective Duke Energy Registrants have control and those variable interest entities (VIEs) where the respective Duke Energy Registrants are the primary beneficiary. These Consolidated Financial Statements also reflect the Duke Energy Registrants' proportionate share of certain generation and transmission facilities. In January 2012, Duke Energy Ohio completed the sale of its 75% ownership of the Vermillion Generating Station (Vermillion); upon the close, Duke Energy Indiana purchased a 62.5% interest in the station. See Note 2 for further discussion. Duke Energy Carolinas, a wholly owned subsidiary of Duke Energy, is an electric utility company that generates, transmits, distributes and sells electricity in North Carolina and South Carolina. Duke Energy Carolinas is subject to the regulatory provisions of the North Carolina Utilities Commission (NCUC), the Public Service Commission of South Carolina (PSCSC), the U.S. Nuclear Regulatory Commission (NRC) and the Federal Energy Regulatory Commission (FERC). Substantially all of Duke Energy Carolinas' operations are regulated and qualify for regulatory accounting treatment. As discussed further in Note 3, Duke Energy Carolinas' operations include one reportable business segment, Franchised Electric. Progress Energy, a wholly owned subsidiary of Duke Energy, is a holding company headquartered in Raleigh, North Carolina, subject to regulation by the FERC. Progress Energy conducts operations through its wholly owned subsidiaries, Progress Energy Carolinas and Progress Energy Florida. As discussed further in Note 3, Progress Energy's operations include one reportable segment, Franchised Electric. Progress Energy Carolinas, an indirect wholly owned subsidiary of Duke Energy, is a regulated public utility primarily engaged in the generation, transmission, distribution and sale of electricity in portions of North Carolina and South Carolina. Progress Energy Carolinas is subject to the regulatory provisions of the NCUC, the PSCSC, the NRC and the FERC. Substantially all of Progress Energy Carolinas' operations are regulated and qualify for regulatory accounting treatment. As discussed further in Note 3, Progress Energy Carolinas' operations include one reportable segment, Franchised Electric. Progress Energy Florida, an indirect wholly owned subsidiary of Duke Energy, is a regulated public utility primarily engaged in the generation, transmission, distribution and sale of electricity in west central Florida. Progress Energy Florida is subject to the regulatory jurisdiction of the Florida Public Service Commission (FPSC), the NRC and the FERC. Substantially all of Progress Energy Florida's operations are regulated and qualify for regulatory accounting treatment. As discussed further in Note 3, Progress Energy Florida's operations include one reportable segment, Franchised Electric. Duke Energy Ohio, an indirect wholly owned subsidiary of Duke Energy, is a combination electric and gas public utility that provides service in the southwestern portion of Ohio and in northern Kentucky through its wholly owned subsidiary, Duke Energy Kentucky, as well as electric generation in parts of Ohio, Illinois and Pennsylvania. Duke Energy Ohio's principal lines of business include generation, transmission and distribution of electricity, the sale of and/or transportation of natural gas, and energy marketing. Duke Energy Ohio conducts competitive auctions for retail electricity supply in Ohio whereby the energy price is recovered from retail customers. Duke Energy Kentucky's principal lines of business include generation, transmission and distribution of electricity, as well as the sale of and/or transportation of natural gas. References herein to Duke Energy Ohio include Duke Energy Ohio and its subsidiaries, unless otherwise noted. Duke Energy Ohio is subject to the regulatory provisions of the Public Utilities Commission of Ohio (PUCO), the Kentucky Public Service Commission (KPSC) and the FERC. Duke Energy Ohio applies regulatory accounting treatment to substantially all of the operations in its Franchised Electric and Gas operating segment. Through November 2011, Duke Energy Ohio applied regulatory accounting treatment to certain rate riders associated with retail generation of its Commercial Power operating segment. See Note 3 for further information about Duke Energy Ohio's business segments. Duke Energy Indiana, an indirect wholly owned subsidiary of Duke Energy, is an electric utility that provides service in north central, central, and southern Indiana. Its primary line of business is generation, transmission and distribution of electricity. Duke Energy Indiana is subject to the regulatory provisions of the Indiana Utility Regulatory Commission (IURC) and the FERC. Substantially all of Duke Energy Indiana's operations are regulated and qualify for regulatory accounting treatment. As discussed further in Note 3, Duke Energy Indiana's operations include one reportable business segment, Franchised Electric. Certain prior year amounts have been reclassified to conform to current year presentation. In addition, prior year financial statements and footnote disclosures for the Progress Energy Registrants have been reclassified to conform to Duke Energy's presentation.
Use Of Estimates	Use of Estimates. To conform to generally accepted accounting principles (GAAP) in the U.S., management makes estimates and assumptions that affect the amounts reported in the Consolidated Financial Statements and Notes. Although these estimates are based on management's best available information at the time, actual results could differ.
Cost-Based Regulation	Cost-Based Regulation. The Duke Energy Registrants account for their regulated operations in accordance with applicable regulatory accounting guidance. The economic effects of regulation can result in a regulated company recording assets for costs that have been or are expected to be approved for recovery from customers in a future period or recording liabilities for amounts that are expected to be returned to customers in the rate-setting process in a period different from the period in which the amounts would be recorded by an unregulated enterprise. Accordingly, the Duke Energy Registrants record assets and liabilities that result from the regulated ratemaking process that would not be recorded under GAAP for nonregulated entities. Regulatory assets and liabilities are amortized consistent with the treatment of the related cost in the ratemaking process. Management continually assesses whether regulatory assets are probable of future recovery by considering factors such as applicable regulatory changes, recent rate orders applicable to other regulated entities and the status of any pending or potential deregulation legislation. Additionally, management continually assesses whether any regulatory liabilities have been incurred. Based on this continual assessment, management believes the existing regulatory assets are probable of recovery and that no regulatory liabilities, other than those recorded, have been incurred. These regulatory assets and liabilities are classified in the Consolidated Balance Sheets as Regulatory assets and Other in Current Assets and as Regulatory liabilities and Other in Current Liabilities, respectively. The Duke Energy Registrants periodically evaluate the applicability of regulatory accounting treatment by considering factors such as regulatory changes and the impact of competition. If cost-based regulation ends or competition increases, the Duke Energy Registrants may have to reduce their asset balances to reflect a market basis less than cost and write-off the associated regulatory assets and liabilities. If it becomes probable that part of the cost of a plant under construction or a recently completed plant will be disallowed for ratemaking purposes and a reasonable estimate of the amount of the disallowance can be made, that amount is recognized as a loss. In November 2011, in conjunction with the PUCO's approval of its new Electric Security Plan (ESP), Duke Energy Ohio ceased applying regulatory accounting treatment to generation operations within its Commercial Power segment. For further information, see Note 4.
Energy Purchases, Fuel Costs And Fuel Cost Deferrals	Energy Purchases, Fuel Costs and Fuel Cost Deferrals. The Duke Energy Registrants utilize cost-tracking mechanisms, commonly referred to as a fuel adjustment clause, to recover the retail portion of fuel and purchased power. The Duke Energy Registrants defer the related cost through Fuel used in electric generation and purchased power — regulated on the Consolidated Statement of Operations, unless a regulatory requirement exists for deferral through Operating Revenues. Fuel used in electric generation and purchased power — regulated includes fuel, purchased power and recoverable costs that are deferred through fuel clauses established by the Subsidiary Registrants' regulators. These clauses allow the Subsidiary Registrants to recover fuel costs, fuel-related costs and portions of purchased power costs through surcharges on customer rates. The Subsidiary Registrants record any under-recovery or over-recovery resulting from the differences between estimated and actual costs as a regulatory asset or regulatory liability until billed or refunded to customers, at which point the differences are adjusted through revenues. Indiana law limits the amount of fuel costs that Duke Energy Indiana can recover to an amount that will not result in earning a return in excess of that allowed by the IURC. As discussed in Note 4, beginning January 1, 2012, Duke Energy Ohio procures energy for its retail customers through a third-party auction. Purchases of energy through the auction process are a pass-through of costs for Duke Energy Ohio, with no affect on earnings. Subsequent to December 31, 2011, Duke Energy Ohio's generation assets are no longer dedicated to retail customers and, accordingly, Duke Energy Ohio can no longer recover their generation assets' energy purchases and fuel costs from regulated customers.
Cash and Cash Equivalents	Cash and Cash Equivalents. All highly liquid investments with maturities of three months or less at the date of acquisition are considered cash equivalents. At December 31, 2012, Duke Energy had cash and cash equivalents of $1,424 million, of which $731 million is held in foreign jurisdictions and is forecasted to be used to fund international operations and investments.
Restricted Cash	Restricted Cash. The Duke Energy Registrants have restricted cash related primarily to collateral assets, escrow deposits, and restricted cash of VIEs. Restricted cash balances are reflected in Other within Current Assets and in Other within Investments and Other Assets on the Consolidated Balance Sheets.
Inventory	Inventory. Inventory is comprised of amounts presented in the tables below and is recorded primarily using the average cost method. Inventory related to the Duke Energy Registrants' regulated operations is valued at historical cost consistent with ratemaking treatment. Materials and supplies are recorded as inventory when purchased and subsequently charged to expense or capitalized to property, plant and equipment when installed. Reserves are established for excess and obsolete inventory. Inventory related to the Duke Energy Registrants' nonregulated operations is valued at the lower of cost or market. The following tables present the Duke Energy Registrants' inventory.
Investments In Debt And Equity Securities	Investments in Debt and Equity Securities. The Duke Energy Registrants classify investments into two categories — trading and available-for-sale. Trading securities are reported at fair value in the Consolidated Balance Sheets with net realized and unrealized gains and losses included in earnings each period. Available-for-sale securities are also reported at fair value on the Consolidated Balance Sheets with unrealized gains and losses included in Accumulated Other Comprehensive Income (AOCI) or as a regulatory asset or liability, unless it is determined that the carrying value of an investment is other-than-temporarily impaired. Other-than-temporary impairments related to equity securities and the credit loss portion of debt securities are included in earnings, unless deferred in accordance with regulatory accounting treatment. Investments in debt and equity securities are classified as either short-term investments or long-term investments based on management's intent and ability to sell these securities, taking into consideration illiquidity factors in the current markets with respect to certain investments that have historically provided for a high degree of liquidity, such as investments in auction rate debt securities. See Note 17 for further information on the investments in debt and equity securities, including investments held in the nuclear decommissioning trust funds (NDTF).
Long-Lived Asset Impairments	Long-Lived Asset Impairments. The Duke Energy Registrants evaluate whether long-lived assets, excluding goodwill, have been impaired when circumstances indicate the carrying value of those assets may not be recoverable. For such long-lived assets, an impairment exists when its carrying value exceeds the sum of estimates of the undiscounted cash flows expected to result from the use and eventual disposition of the asset. When alternative courses of action to recover the carrying amount of a long-lived asset are under consideration, a probability-weighted approach is used for developing estimates of future undiscounted cash flows. If the carrying value of the long-lived asset is not recoverable based on these estimated future undiscounted cash flows, the impairment loss is measured as the excess of the carrying value of the asset over its fair value, such that the asset's carrying value is adjusted to its estimated fair value. Management assesses the fair value of long-lived assets using commonly accepted techniques, and may use more than one source. Sources to determine fair value include, but are not limited to, recent third party comparable sales, internally developed discounted cash flow analysis and analysis from outside advisors. Significant changes in market conditions resulting from events such as, among others, changes in commodity prices or the condition of an asset, or a change in management's intent to utilize the asset are generally viewed by management as triggering events to re-assess the cash flows related to the long-lived assets. See Note 12 for further information.
Property, Plant and Equipment	Property, Plant and Equipment. Property, plant and equipment are stated at the lower of historical cost less accumulated depreciation or fair value, if impaired. The Duke Energy Registrants capitalize all construction-related direct labor and material costs, as well as indirect construction costs. Indirect costs include general engineering, taxes and the allowance for funds used during construction (AFUDC). See “AFUDC and Interest Capitalized,” below for additional information. The cost of renewals and betterments that extend the useful life of property, plant and equipment are also capitalized. The cost of repairs, replacements and major maintenance projects, which do not extend the useful life or increase the expected output of the asset, are expensed as incurred. Depreciation is generally computed over the estimated useful life of the asset using the composite straight-line method. For regulated operations, depreciation studies are conducted periodically to update the composite rates and are approved by the various state commissions. The composite weighted-average depreciation rates, excluding nuclear fuel, for each of the Duke Energy Registrants are included in the following table: When the Duke Energy Registrants retire regulated property, plant and equipment under what is considered a normal retirement, the original cost plus the cost of retirement, less salvage value, is charged to accumulated depreciation, consistent with regulated rate-making practices. When it becomes probable that a regulated generation asset will be retired substantially in advance of its original expected useful life or is abandoned, the cost of the asset and the corresponding accumulated depreciation is removed from Cost and Accumulated depreciation and amortization within Property, Plant and Equipment on the Consolidated Balance Sheets and a separate asset is recognized. If the plant is still in operation, the amount is classified as Generation facilities to be retired, net on the Consolidated Balance Sheets. If the plant is no longer operating, then a regulatory asset is recognized. The carrying value of the asset is based on historical cost if the Duke Energy Registrants are allowed to recover the remaining net book value and a full return on the asset. If the Duke Energy Registrants do not expect to recover the full remaining cost and a full return, the carrying value of the asset is based on the lower of cost or the present value of the future revenues expected to be provided to recover the allowable costs discounted at the Duke Energy Registrants' incremental borrowing rate. An impairment is recognized if the net book value of the asset exceeds the present value of the future revenues to be recovered in rates. When the Duke Energy Registrants sell entire regulated operating units, or retire or sell nonregulated properties, the original cost is removed from property and the related accumulated depreciation and amortization balances are reduced. Any gain or loss is recorded in earnings, unless otherwise required by the applicable regulatory body. See Note 10 for further information on the components and estimated useful lives of Duke Energy's property, plant and equipment.
Nuclear Fuel	Nuclear Fuel. Nuclear fuel is classified as Property, Plant and Equipment in the Consolidated Balance Sheets. Nuclear fuel in the front-end fuel processing phase is considered work in progress and not amortized until placed in service. Amortization of nuclear fuel is included within Fuel used in electric generation and purchased power-regulated in the Consolidated Statements of Operations. The amortization is recorded using the units-of-production method.
AFUDC And Interest Capitalized	AFUDC and Interest Capitalized. In accordance with applicable regulatory accounting guidance, the Duke Energy Registrants record AFUDC, which represents the estimated debt and equity costs of capital funds necessary to finance the construction of new regulated facilities. The equity component of AFUDC is a non-cash amount within the Consolidated Statements of Operations. AFUDC is capitalized as a component of the cost of property, plant and equipment, with an offsetting credit to Other income and expenses, net on the Consolidated Statements of Operations for the equity component and as an offset to Interest Expense on the Consolidated Statements of Operations for the debt component. After construction is completed, the Duke Energy Registrants are permitted to recover these costs through inclusion in the rate base and the corresponding depreciation expense or nuclear fuel expense. AFUDC equity is a permanent difference item for income tax purposes, thus reducing the Duke Energy Registrants' effective tax rate during the construction phase in which AFUDC equity is being recorded. The effective tax rate is subsequently increased in future periods when the completed property, plant and equipment are placed in service and depreciation of the AFUDC equity commences. See Note 24 for information related to the impacts of AFUDC equity on the Duke Energy Registrants' effective tax rate. For nonregulated operations, interest is capitalized during the construction phase in accordance with the applicable accounting guidance.
Asset Retirement Obligations	Asset Retirement Obligations. The Duke Energy Registrants recognize asset retirement obligations for legal obligations associated with the retirement of long-lived assets that result from the acquisition, construction, development and/or normal use of the asset, and for conditional asset retirement obligations. The term conditional asset retirement obligation refers to a legal obligation to perform an asset retirement activity in which the timing and (or) method of settlement are conditional on a future event that may or may not be within the control of the entity. The obligation to perform the asset retirement activity is unconditional even though uncertainty exists about the timing and (or) method of settlement. Thus, the timing and (or) method of settlement may be conditional on a future event. When recording an asset retirement obligation, the present value of the projected liability is recognized in the period in which it is incurred, if a reasonable estimate of fair value can be made. The liability is then accreted over time by applying an interest method of allocation to the liability. Substantially all accretion is related to regulated operations and is deferred pursuant to regulatory accounting. The present value of the liability is added to the carrying amount of the associated asset and this additional carrying amount is depreciated over the remaining life of the asset. The present value of the initial obligation and subsequent updates are based on discounted cash flows, which include estimates regarding the timing of future cash flows, the selection of discount rates and cost escalation rates, among other factors. These underlying assumptions and estimates are made as of a point in time and are subject to change. The obligations for nuclear decommissioning are based on site-specific cost studies. Duke Energy Carolinas and Progress Energy Carolinas assume prompt dismantlement of the nuclear facilities, which reflects dismantling the site after operations are ceased. Progress Energy Florida assumes the nuclear facility will be placed into a safe storage configuration until the eventual dismantling of the site begins in approximately 40-60 years. The nuclear decommissioning asset retirement obligation also assumes Duke Energy Carolinas, Progress Energy Carolinas and Progress Energy Florida will store spent fuel on site until such time that it can be transferred to a U.S. Department of Energy (DOE) facility. See Note 9 for further information.
Unbilled Revenue	Revenue Recognition and Unbilled Revenue. Revenues on sales of electricity and gas are recognized when either the service is provided or the product is delivered. Unbilled retail revenues are estimated by applying average revenue per kilowatt-hour (kWh) or per thousand cubic feet (Mcf) for all customer classes to the number of estimated kWh or Mcf delivered but not billed. Unbilled wholesale energy revenues are calculated by applying the contractual rate per megawatt-hour (MWh) to the number of estimated MWh delivered but not yet billed. Unbilled wholesale demand revenues are calculated by applying the contractual rate per megawatt (MW) to the MW volume delivered but not yet billed. The amount of unbilled revenues can vary significantly from period to period as a result of numerous factors, including seasonality, weather, customer usage patterns and customer mix. The Duke Energy Registrants had unbilled revenues within Receivables and within Restricted receivables of variable interest entities on their respective Consolidated Balance Sheets as shown in the table below.
Accounting For Risk Management, Hedging Activities And Financial Instruments	Accounting for Risk Management, Hedging Activities and Financial Instruments. The Duke Energy Registrants may use a number of different derivative and non-derivative instruments in connection with their commodity price, interest rate and foreign currency risk management activities, including swaps, futures, forwards and options. All derivative instruments except those that qualify for the normal purchase/normal sale (NPNS) exception within the accounting guidance for derivatives are recorded on the Consolidated Balance Sheets at their fair value. The effective portion of the change in the fair value of derivative instruments designated as cash flow hedges is recorded in AOCI. The effective portion of the change in the fair value of a fair value hedge is offset in net income by changes in the hedged item. The Duke Energy Registrants may designate qualifying derivative instruments as either cash flow hedges or fair value hedges, while others either have not been designated as hedges or do not qualify as a hedge (hereinafter referred to as undesignated contracts). For all contracts accounted for as a hedge, the Duke Energy Registrants prepare formal documentation of the hedge in accordance with the accounting guidance for derivatives. In addition, at inception and at least every three months thereafter, the Duke Energy Registrants formally assess whether the hedge contract is highly effective in offsetting changes in cash flows or fair values of hedged items. The Duke Energy Registrants document hedging activity by transaction type and risk management strategy. See Note 15 for further information.
Captive Insurance Reserves	Captive Insurance Reserves. Duke Energy has captive insurance subsidiaries that provide coverage, on an indemnity basis, to the Subsidiary Registrants as well as certain third parties, on a limited basis, for various business risks and losses, such as property, business interruption, workers' compensation and general liability. Liabilities include provisions for estimated losses incurred but not yet reported (IBNR), as well as provisions for known claims which have been estimated on a claims-incurred basis. IBNR reserve estimates involve the use of assumptions and are primarily based upon historical loss experience, industry data and other actuarial assumptions. Reserve estimates are adjusted in future periods as actual losses differ from historical experience. Duke Energy, through its captive insurance entities, also has reinsurance coverage with third parties, which provides reimbursement for certain losses above a per occurrence and/or aggregate retention. Duke Energy recognizes a reinsurance receivable for recovery of incurred losses under its captive's reinsurance coverage once realization of the receivable is deemed probable.
Unamortized Debt Premium, Discount And Expense	Unamortized Debt Premium, Discount and Expense. Premiums, discounts and expenses incurred with the issuance of outstanding long-term debt are amortized over the terms of the debt issues. Any call premiums or unamortized expenses associated with refinancing higher-cost debt obligations used to finance regulated assets and operations are amortized consistent with regulatory treatment of those items, where appropriate. The amortization expense is recorded as a component of Interest Expense in the Consolidated Statements of Operations and is reflected as Depreciation, amortization and accretion within Net cash provided by operating activities on the Consolidated Statements of Cash Flows.
Loss Contingencies And Environmental Liabilities	Loss Contingencies and Environmental Liabilities. The Duke Energy Registrants are involved in certain legal and environmental matters that arise in the normal course of business. Contingent losses are recorded when it is determined that it is probable that a loss has occurred and the amount of the loss can be reasonably estimated. When a range of the probable loss exists and no amount within the range is a better estimate than any other amount, the Duke Energy Registrants record a loss contingency at the minimum amount in the range. Unless otherwise required by GAAP, legal fees are expensed as incurred. Environmental liabilities are recorded on an undiscounted basis when the necessity for environmental remediation becomes probable and the costs can be reasonably estimated, or when other potential environmental liabilities are reasonably estimable and probable. The Duke Energy Registrants expense environmental expenditures related to conditions caused by past operations that do not generate current or future revenues. Certain environmental expenses receive regulatory accounting treatment, under which the expenses are recorded as regulatory assets. Environmental expenditures related to operations that generate current or future revenues are expensed or capitalized, as appropriate. See Note 5 for further information.
Pension And Other Post-Retirement Benefit Plans	Pension and Other Post-Retirement Benefit Plans. Duke Energy maintains qualified, non-qualified and other post-retirement benefit plans. Eligible employees of the Subsidiary Registrants participate in the respective Duke Energy or Progress Energy qualified, non-qualified and other post-retirement benefit plans and are allocated their proportionate share of benefit costs. See Note 23 for information related to Duke Energy's benefit plans, including certain accounting policies associated with these plans.
Severance And Special Termination Benefits	Severance and Special Termination Benefits. Duke Energy has an ongoing severance plan under which, in general, the longer a terminated employee worked prior to termination the greater the amount of severance benefits. The Duke Energy Registrants record a liability for involuntary severance once an involuntary severance plan is committed to by management, or sooner, if involuntary severances are probable and the related severance benefits can be reasonably estimated. For involuntary severance benefits that are incremental to its ongoing severance plan benefits, Duke Energy measures the obligation and records the expense at its fair value at the communication date if there are no future service requirements, or, if future service is required to receive the termination benefit, ratably over the service period. From time to time, Duke Energy offers special termination benefits under voluntary severance programs. Special termination benefits are measured upon employee acceptance and recorded immediately absent a significant retention period. If a significant retention period exists, the cost of the special termination benefits are recorded ratably over the remaining service periods of the affected employees. Employee acceptance of voluntary severance benefits is determined by management based on the facts and circumstances of the special termination benefits being offered. See Note 21 for further information.
Guarantees	Guarantees. Upon issuance or modification of a guarantee, the Duke Energy Registrants recognize a liability at the time of issuance or material modification for the estimated fair value of the obligation it assumes under that guarantee, if any. Fair value is estimated using a probability-weighted approach. The Duke Energy Registrants reduce the obligation over the term of the guarantee or related contract in a systematic and rational method as risk is reduced under the obligation. Any additional contingent loss for guarantee contracts subsequent to the initial recognition of a liability in accordance with applicable accounting guidance is accounted for and recognized at the time a loss is probable and the amount of the loss can be reasonably estimated. The Duke Energy Registrants have entered into various indemnification agreements related to purchase and sale agreements and other types of contractual agreements with vendors and other third parties. These agreements typically cover environmental, tax, litigation and other matters, as well as breaches of representations, warranties and covenants. Typically, claims may be made by third parties for various periods of time, depending on the nature of the claim. Potential exposure under these indemnification agreements can range from a specified to an unlimited dollar amount, depending on the nature of the claim and the particular transaction. See Note 7 for further information.
Stock-based Compensation	Stock-Based Compensation. Stock-based compensation represents the cost related to stock-based awards granted to employees. Duke Energy recognizes stock-based compensation based upon the estimated fair value of the awards, net of estimated forfeitures. The recognition period for these costs begin at either the applicable service inception date or grant date and continues throughout the requisite service period, or for certain share-based awards until the employee becomes retirement eligible, if earlier. Share-based awards, including stock options, but not performance shares, granted to employees that are already retirement eligible are deemed to have vested immediately upon issuance, and, therefore, compensation cost for those awards is recognized on the date such awards are granted. See Note 22 for further information.
Accounting For Purchases And Sales Of Emission Allowances	Accounting For Purchases and Sales of Emission Allowances. Emission allowances are issued by the Environmental Protection Agency (EPA) at zero cost and permit the holder of the allowance to emit certain gaseous by-products of fossil fuel combustion, including sulfur dioxide (SO2) and nitrogen oxide (NOx). Allowances may also be bought and sold via third-party transactions. Allowances allocated to or acquired by the Duke Energy Registrants are held primarily for consumption. Emission allowances at cost are included in Intangibles, net on the Consolidated Balance Sheets and the Duke Energy Registrants recognize expense as the allowances are consumed or sold. Gains or losses on sales of emission allowances by regulated businesses that do not provide for direct recovery through a cost-tracking mechanism and by nonregulated businesses are presented in Gains on Sales of Other Assets and Other, net, in the Consolidated Statements of Operations. For regulated businesses that provide for direct recovery of emission allowances, any gain or loss on sales of recoverable emission allowances are included in the rate structure of the regulated entity and are deferred as a regulatory asset or liability. Future rates charged to retail customers are impacted by any gain or loss on sales of recoverable emission allowances. Purchases and sales of emission allowances are presented gross as investing activities on the Consolidated Statements of Cash Flows. See Note 12 for discussion regarding the impairment of the carrying value of certain emission allowances in 2011.
Income Taxes	Income Taxes. Duke Energy and its subsidiaries file a consolidated federal income tax return and other state and foreign jurisdictional returns as required. Deferred income taxes have been provided for temporary differences between the GAAP and tax carrying amounts of assets and liabilities. These differences create taxable or tax-deductible amounts for future periods. Investment tax credits (ITC) associated with regulated operations are deferred and are amortized as a reduction of income tax expense over the estimated useful lives of the related properties. The Subsidiary Registrants entered into a tax sharing agreement with Duke Energy, where the separate return method is used to allocate tax expenses and benefits to the subsidiaries whose investments or results of operations provide these tax expenses or benefits. The accounting for income taxes essentially represents the income taxes that the Subsidiary Registrants would incur if the Subsidiary Registrants were a separate company filing its own federal tax return as a C-Corporation. The Duke Energy Registrants record unrecognized tax benefits for positions taken or expected to be taken on tax returns, including the decision to exclude certain income or transactions from a return, when a more-likely-than-not threshold is met for a tax position and management believes that the position will be sustained upon examination by the taxing authorities. Management evaluates each position based solely on the technical merits and facts and circumstances of the position, assuming the position will be examined by a taxing authority having full knowledge of all relevant information. The Duke Energy Registrants record the largest amount of the unrecognized tax benefit that is greater than 50% likely of being realized upon settlement or effective settlement. Management considers a tax position effectively settled for the purpose of recognizing previously unrecognized tax benefits when the following conditions exist: (i) the taxing authority has completed its examination procedures, including all appeals and administrative reviews that the taxing authority is required and expected to perform for the tax positions, (ii) the Duke Energy Registrants do not intend to appeal or litigate any aspect of the tax position included in the completed examination, and (iii) it is remote that the taxing authority would examine or reexamine any aspect of the tax position. Deferred taxes are not provided on translation gains and losses where Duke Energy expects earnings of a foreign operation to be indefinitely reinvested. The Duke Energy Registrants record tax-related interest expense in Interest Expense and interest income and penalties in Other Income and Expenses, net, in the Consolidated Statements of Operations. See Note 24 for further information.
Excise Taxes	Excise Taxes. Certain excise taxes levied by state or local governments are collected by the Duke Energy Registrants from their customers. These taxes, which are required to be paid regardless of the Duke Energy Registrants' ability to collect from the customer, are accounted for on a gross basis. When the Duke Energy Registrants act as an agent, and the tax is not required to be remitted if it is not collected from the customer, the taxes are accounted for on a net basis. The Duke Energy Registrants' excise taxes accounted for on a gross basis and recorded as operating revenues in the Consolidated Statements of Operations were as follows:
Foreign Currency Transaction	Foreign Currency Translation. The local currencies of Duke Energy's foreign operations have been determined to be their functional currencies, except for certain foreign operations whose functional currency has been determined to be the U.S. Dollar, based on an assessment of the economic circumstances of the foreign operation. Assets and liabilities of foreign operations, except for those whose functional currency is the U.S. Dollar, are translated into U.S. Dollars at the exchange rates in effect at period end. Translation adjustments resulting from fluctuations in exchange rates are included as a separate component of AOCI. Revenue and expense accounts of these operations are translated at average exchange rates prevailing during the year. Gains and losses arising from balances and transactions denominated in currencies other than the functional currency are included in the results of operations in the period in which they occur.
Dividend Restrictions And Unappropriated Retained Earnings	Dividend Restrictions and Unappropriated Retained Earnings. Duke Energy does not have any legal, regulatory or other restrictions on paying common stock dividends to shareholders. However, as further described in Note 4, due to conditions established by regulators at the time of the Duke Energy/Cinergy merger in April 2006 and the Duke Energy/Progress Energy merger in 2012, certain wholly owned subsidiaries, including Duke Energy Carolinas, Progress Energy Carolinas, Duke Energy Ohio and Duke Energy Indiana, have restrictions on paying dividends or otherwise advancing funds to Duke Energy. At December 31, 2012 and 2011, an insignificant amount of Duke Energy's consolidated Retained earnings balance represents undistributed earnings of equity method investments.
New Accounting Standards [Policy Text Block]	New Accounting Standards. The following new accounting standards were adopted by the Duke Energy Registrants during the year ended December 31, 2012, and the impact of such adoption, if applicable, has been presented in the accompanying Consolidated Financial Statements: Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC) 220 — Comprehensive Income. In June 2011, the FASB amended the existing requirements for presenting comprehensive income in financial statements primarily to increase the prominence of items reported in other comprehensive income (OCI) and to facilitate the convergence of U.S. GAAP and International Financial Reporting Standards (IFRS). Specifically, the revised guidance eliminates the option previously provided to present components of OCI as part of the statement of changes in stockholders' equity. Accordingly, all non-owner changes in stockholders' equity are required to be presented either in a single continuous statement of comprehensive income or in two separate but consecutive financial statements. For the Duke Energy Registrants, this revised guidance was effective on a retrospective basis for interim and annual periods beginning January 1, 2012. The adoption of this standard changed the presentation of the Duke Energy Registrants' financial statements but did not affect the calculation of net income, comprehensive income or earnings per share. ASC 820 — Fair Value Measurements and Disclosures. In May 2011, the FASB amended existing requirements for measuring fair value and for disclosing information about fair value measurements. This revised guidance results in a consistent definition of fair value, as well as common requirements for measurement and disclosure of fair value information between U.S. GAAP and IFRS. In addition, the amendments set forth enhanced disclosure requirements with respect to recurring Level 3 measurements, nonfinancial assets measured or disclosed at fair value, transfers between levels in the fair value hierarchy, and assets and liabilities disclosed but not recorded at fair value. For the Duke Energy Registrants, the revised fair value measurement guidance was effective on a prospective basis for interim and annual periods beginning January 1, 2012. The adoption of this new guidance did not have a significant impact on the Duke Energy Registrants disclosures or their consolidated results of operations, cash flows, or financial position. The following new accounting standards were adopted by Duke Energy during the year ended December 31, 2011, and the impact of such adoption, if applicable has been presented in the accompanying Consolidated Financial Statements: ASC 605 — Revenue Recognition. In October 2009, the FASB issued new revenue recognition accounting guidance in response to practice concerns related to the accounting for revenue arrangements with multiple deliverables. This new accounting guidance primarily applies to all contractual arrangements in which a vendor will perform multiple revenue generating activities and addresses the unit of accounting for arrangements involving multiple deliverables, as well as how arrangement consideration should be allocated to the separate units of accounting. For the Duke Energy Registrants, the new accounting guidance was effective January 1, 2011, and applied on a prospective basis. This new accounting guidance did not have a material impact to the consolidated results of operations, cash flows or financial position of the Duke Energy Registrants. ASC 805 — Business Combinations. In November 2010, the FASB issued new accounting guidance in response to diversity in the interpretation of pro forma information disclosure requirements for business combinations. The new accounting guidance requires an entity to present pro forma financial information as if a business combination occurred at the beginning of the earliest period presented as well as additional disclosures describing the nature and amount of material, nonrecurring pro forma adjustments. This new accounting guidance was effective January 1, 2011, and has been applied to all business combinations consummated after that date. ASC 820 — Fair Value Measurements and Disclosures. In January 2010, the FASB amended existing fair value measurements and disclosures accounting guidance to clarify certain existing disclosure requirements and to require a number of additional disclosures, including amounts and reasons for significant transfers between the three levels of the fair value hierarchy, and presentation of certain information in the reconciliation of recurring Level 3 measurements on a gross basis. For the Duke Energy Registrants, certain portions of this revised accounting guidance were effective on January 1, 2010, with additional disclosures effective for periods beginning January 1, 2011. The adoption of this accounting guidance resulted in additional disclosure in the notes to the consolidated financial statements but did not have an impact on the Duke Energy Registrants' consolidated results of operations, cash flows or financial position. ASC 350 — Intangibles–Goodwill and Other. In September 2011, the FASB amended existing goodwill impairment testing accounting guidance to provide an entity testing goodwill for impairment with the option of performing a qualitative assessment prior to calculating the fair value of a reporting unit in step one of a goodwill impairment test. Under this revised guidance, a qualitative assessment would require an evaluation of economic, industry, and company-specific considerations. If an entity determines, on a basis of such qualitative factors, that the fair value of a reporting unit is more likely than not less than the carrying value of a reporting unit, the two-step impairment test, as required under pre-existing applicable accounting guidance, would be required. Otherwise, no further impairment testing would be required. The revised goodwill impairment testing accounting guidance is effective for the Duke Energy Registrants' annual and interim goodwill impairment tests performed for fiscal years beginning January 1, 2012, with early adoption of this revised guidance permitted for annual and interim goodwill impairment tests performed as of a date before September 15, 2011. Since annual goodwill impairment tests are performed by Duke Energy as of August 31, the Duke Energy Registrants early adopted this revised accounting guidance during the third quarter of 2011 and applied that guidance to their annual goodwill impairment tests for 2011. The following new accounting standards were adopted by Duke Energy during the year ended December 31, 2010, and the impact of such adoption, if applicable has been presented in the accompanying Consolidated Financial Statements: ASC 860 — Transfers and Servicing. In June 2009, the FASB issued revised accounting guidance for transfers and servicing of financial assets and extinguishment of liabilities, to require additional information about transfers of financial assets, including securitization transactions, as well as additional information about an enterprise's continuing exposure to the risks related to transferred financial assets. This revised accounting guidance eliminated the concept of a Qualifying Special Purpose Entity (QSPE) and required those entities which were not subject to consolidation under previous accounting rules to now be assessed for consolidation. In addition, this accounting guidance clarified and amended the derecognition criteria for transfers of financial assets (including transfers of portions of financial assets) and required additional disclosures about a transferor's continuing involvement in transferred financial assets. For Duke Energy, this revised accounting guidance was effective prospectively for transfers of financial assets occurring on or after January 1, 2010, and early adoption of this statement was prohibited. Since 2002, Duke Energy Ohio, Duke Energy Indiana, and Duke Energy Kentucky have sold, on a revolving basis, nearly all of their accounts receivable and related collections through CRC, a bankruptcy-remote QSPE. The securitization transaction was structured to meet the criteria for sale accounting treatment, and, accordingly, Duke Energy did not consolidate CRC, and the transfers were accounted for as sales. Effective with adoption of this revised accounting guidance and ASC 810-Consolidation, as discussed below, the accounting treatment and/or financial statement presentation of Duke Energy's accounts receivable securitization programs was impacted as Duke Energy began consolidating CRC effective January 1, 2010. Duke Energy Ohio's and Duke Energy Indiana's sales of accounts receivable and related financial statement presentation were not impacted by the adoption of ASC 860. ASC 810 — Consolidations. In June 2009, the FASB amended existing consolidation accounting guidance to eliminate the exemption from consolidation for QSPEs, and clarified, but did not significantly change, the criteria for determining whether an entity meets the definition of a VIE. This revised accounting guidance also required an enterprise to qualitatively assess the determination of the primary beneficiary of a VIE based on whether that enterprise has both the power to direct the activities that most significantly impact the economic performance of a VIE and the obligation to absorb losses or the right to receive benefits of a VIE that could potentially be significant to a VIE. In addition, this revised accounting guidance modified existing accounting guidance to require an ongoing evaluation of a VIE's primary beneficiary and amended the types of events that trigger a reassessment of whether an entity is a VIE. Furthermore, this accounting guidance required enterprises to provide additional disclosures about their involvement with VIEs and any significant changes in their risk exposure due to that involvement. For the Duke Energy Registrants, this accounting guidance was effective beginning on January 1, 2010, and is applicable to all entities in which Duke Energy is involved, including entities previously subject to existing accounting guidance for VIEs, as well as any QSPEs that existed as of the effective date. Effective with adoption of this revised accounting guidance, the accounting treatment and/or financial statement presentation of Duke Energy's accounts receivable securitization programs were impacted as Duke Energy began consolidating CRC effective January 1, 2010. Duke Energy Ohio's and Duke Energy Indiana's sales of accounts receivable and related financial statement presentation were not impacted by the adoption of ASC 810. This revised accounting guidance did not have a significant impact on any of the Duke Energy Registrants' other interests in VIEs. ASC 820 — Fair Value Measurements and Disclosures. In January 2010, the FASB amended existing fair value measurements and disclosures accounting guidance to clarify certain existing disclosure requirements and to require a number of additional disclosures, including amounts and reasons for significant transfers between the three levels of the fair value hierarchy, and presentation of certain information in the reconciliation of recurring Level 3 measurements on a gross basis. For the Duke Energy Registrants, certain portions of this revised accounting guidance were effective on January 1, 2010, with additional disclosures effective for periods beginning January 1, 2011. The initial adoption of this accounting guidance resulted in additional disclosure in the notes to the consolidated financial statements but did not have an impact on the Duke Energy Registrants' consolidated results of operations, cash flows or financial position. The following new Accounting Standards Updates (ASU) have been issued, but have not yet been adopted by Duke Energy, as of December 31, 2012. ASC 210 — Balance Sheet. In December 2011, the FASB issued revised accounting guidance to amend the existing disclosure requirements for offsetting financial assets and liabilities to enhance current disclosures, as well as to improve comparability of balance sheets prepared under U.S. GAAP and IFRS. The revised disclosure guidance affects all companies that have financial instruments and derivative instruments that are either offset in the balance sheet (i.e., presented on a net basis) or subject to an enforceable master netting arrangement and/or similar agreement. The revised guidance requires that certain enhanced quantitative and qualitative disclosures be made with respect to a company's netting arrangements and/or rights of setoff associated with its financial instruments and/or derivative instruments including associated collateral. For the Duke Energy Registrants, the revised disclosure guidance is effective on a retrospective basis for interim and annual periods beginning January 1, 2013. Other than additional disclosures, this revised guidance does not impact the Duke Energy Registrants' consolidated results of operations, cash flows or financial position. ASC 220 — Comprehensive Income. In February 2013, the FASB amended the existing requirements for presenting comprehensive income in financial statements to improve the reporting of reclassifications out of AOCI. The amendments in this Update seek to attain that objective by requiring an entity to report the effect of significant reclassifications out of AOCI on the respective line items in net income if the amount being reclassified is required under U.S. GAAP to be reclassified in its entirety to net income. For other amounts that are not required under U.S. GAAP to be reclassified in their entirety to net income in the same reporting period, an entity is required to cross-reference other disclosures required under U.S. GAAP that provide additional detail about those amounts. This would be the case when a portion of the amount reclassified out of AOCI is reclassified to a balance sheet account (for example, inventory) instead of directly to income or expense in the same reporting period. For the Duke Energy Registrants, this revised guidance is effective on a prospective basis for interim and annual periods beginning January 1, 2013. Other than additional disclosures or a change in the presentation on the statement of comprehensive income, this revised guidance does not impact the Duke Energy Registrants' consolidated results of operations, cash flows or financial position.
Progress Energy [Member]
Policy Text Block [Line Items]
Organization	Nature of Operations and Basis of Consolidation. Duke Energy Corporation (collectively with its subsidiaries, Duke Energy), is an energy company headquartered in Charlotte, North Carolina. Duke Energy operates in the United States (U.S.) and Latin America primarily through its direct and indirect subsidiaries. Duke Energy's subsidiaries included Duke Energy Carolinas, LLC (Duke Energy Carolinas), Duke Energy Ohio, Inc. (Duke Energy Ohio), which includes Duke Energy Kentucky, Inc. (Duke Energy Kentucky), and Duke Energy Indiana, Inc. (Duke Energy Indiana) prior to the merger with Progress Energy, Inc. (Progress Energy). On July 2, 2012, Duke Energy merged with Progress Energy, with Duke Energy continuing as the surviving corporation, and Progress Energy becoming a subsidiary of Duke Energy. Carolina Power & Light Company d/b/a Progress Energy Carolinas, Inc. (Progress Energy Carolinas) and Florida Power Corporation d/b/a Progress Energy Florida, Inc. (Progress Energy Florida), Progress Energy's regulated utility subsidiaries, are now indirect subsidiaries of Duke Energy. Duke Energy's consolidated financial statements include Progress Energy, Progress Energy Carolinas and Progress Energy Florida activity beginning July 2, 2012. See Note 2 for additional information regarding the merger. When discussing Duke Energy's consolidated financial information, it necessarily includes the results of its six separate subsidiary registrants, Duke Energy Carolinas, Progress Energy, Progress Energy Carolinas, Progress Energy Florida, Duke Energy Ohio and Duke Energy Indiana (collectively referred to as the Subsidiary Registrants), which, along with Duke Energy, are collectively referred to as the Duke Energy Registrants. Progress Energy, Progress Energy Carolinas and Progress Energy Florida (collectively referred to as the Progress Energy Registrants) continue to maintain reporting requirements as SEC registrants. In accordance with SEC guidance, the Progress Energy Registrants did not reflect the impacts of acquisition accounting from the merger with Duke Energy, whereby the adjustments of assets and liabilities to fair value and the resultant goodwill would be shown on the financial statements of the Progress Energy Registrants. These adjustments were recorded by Duke Energy. The information in these combined notes relates to each of the Duke Energy Registrants as noted in the Index to the Combined Notes. However, none of the registrants makes any representation as to information related solely to Duke Energy or the subsidiaries of Duke Energy other than itself. As discussed further in Note 3, Duke Energy operates three reportable business segments: U.S. Franchised Electric and Gas (USFE&G), Commercial Power and International Energy. The remainder of Duke Energy's operations is presented as Other. These Consolidated Financial Statements include, after eliminating intercompany transactions and balances, the accounts of the Duke Energy Registrants and all majority-owned subsidiaries where the respective Duke Energy Registrants have control and those variable interest entities (VIEs) where the respective Duke Energy Registrants are the primary beneficiary. These Consolidated Financial Statements also reflect the Duke Energy Registrants' proportionate share of certain generation and transmission facilities. In January 2012, Duke Energy Ohio completed the sale of its 75% ownership of the Vermillion Generating Station (Vermillion); upon the close, Duke Energy Indiana purchased a 62.5% interest in the station. See Note 2 for further discussion. Duke Energy Carolinas, a wholly owned subsidiary of Duke Energy, is an electric utility company that generates, transmits, distributes and sells electricity in North Carolina and South Carolina. Duke Energy Carolinas is subject to the regulatory provisions of the North Carolina Utilities Commission (NCUC), the Public Service Commission of South Carolina (PSCSC), the U.S. Nuclear Regulatory Commission (NRC) and the Federal Energy Regulatory Commission (FERC). Substantially all of Duke Energy Carolinas' operations are regulated and qualify for regulatory accounting treatment. As discussed further in Note 3, Duke Energy Carolinas' operations include one reportable business segment, Franchised Electric. Progress Energy, a wholly owned subsidiary of Duke Energy, is a holding company headquartered in Raleigh, North Carolina, subject to regulation by the FERC. Progress Energy conducts operations through its wholly owned subsidiaries, Progress Energy Carolinas and Progress Energy Florida. As discussed further in Note 3, Progress Energy's operations include one reportable segment, Franchised Electric. Progress Energy Carolinas, an indirect wholly owned subsidiary of Duke Energy, is a regulated public utility primarily engaged in the generation, transmission, distribution and sale of electricity in portions of North Carolina and South Carolina. Progress Energy Carolinas is subject to the regulatory provisions of the NCUC, the PSCSC, the NRC and the FERC. Substantially all of Progress Energy Carolinas' operations are regulated and qualify for regulatory accounting treatment. As discussed further in Note 3, Progress Energy Carolinas' operations include one reportable segment, Franchised Electric. Progress Energy Florida, an indirect wholly owned subsidiary of Duke Energy, is a regulated public utility primarily engaged in the generation, transmission, distribution and sale of electricity in west central Florida. Progress Energy Florida is subject to the regulatory jurisdiction of the Florida Public Service Commission (FPSC), the NRC and the FERC. Substantially all of Progress Energy Florida's operations are regulated and qualify for regulatory accounting treatment. As discussed further in Note 3, Progress Energy Florida's operations include one reportable segment, Franchised Electric. Duke Energy Ohio, an indirect wholly owned subsidiary of Duke Energy, is a combination electric and gas public utility that provides service in the southwestern portion of Ohio and in northern Kentucky through its wholly owned subsidiary, Duke Energy Kentucky, as well as electric generation in parts of Ohio, Illinois and Pennsylvania. Duke Energy Ohio's principal lines of business include generation, transmission and distribution of electricity, the sale of and/or transportation of natural gas, and energy marketing. Duke Energy Ohio conducts competitive auctions for retail electricity supply in Ohio whereby the energy price is recovered from retail customers. Duke Energy Kentucky's principal lines of business include generation, transmission and distribution of electricity, as well as the sale of and/or transportation of natural gas. References herein to Duke Energy Ohio include Duke Energy Ohio and its subsidiaries, unless otherwise noted. Duke Energy Ohio is subject to the regulatory provisions of the Public Utilities Commission of Ohio (PUCO), the Kentucky Public Service Commission (KPSC) and the FERC. Duke Energy Ohio applies regulatory accounting treatment to substantially all of the operations in its Franchised Electric and Gas operating segment. Through November 2011, Duke Energy Ohio applied regulatory accounting treatment to certain rate riders associated with retail generation of its Commercial Power operating segment. See Note 3 for further information about Duke Energy Ohio's business segments. Duke Energy Indiana, an indirect wholly owned subsidiary of Duke Energy, is an electric utility that provides service in north central, central, and southern Indiana. Its primary line of business is generation, transmission and distribution of electricity. Duke Energy Indiana is subject to the regulatory provisions of the Indiana Utility Regulatory Commission (IURC) and the FERC. Substantially all of Duke Energy Indiana's operations are regulated and qualify for regulatory accounting treatment. As discussed further in Note 3, Duke Energy Indiana's operations include one reportable business segment, Franchised Electric. Certain prior year amounts have been reclassified to conform to current year presentation. In addition, prior year financial statements and footnote disclosures for the Progress Energy Registrants have been reclassified to conform to Duke Energy's presentation.
Use Of Estimates	Use of Estimates. To conform to generally accepted accounting principles (GAAP) in the U.S., management makes estimates and assumptions that affect the amounts reported in the Consolidated Financial Statements and Notes. Although these estimates are based on management's best available information at the time, actual results could differ.
Cost-Based Regulation	Cost-Based Regulation. The Duke Energy Registrants account for their regulated operations in accordance with applicable regulatory accounting guidance. The economic effects of regulation can result in a regulated company recording assets for costs that have been or are expected to be approved for recovery from customers in a future period or recording liabilities for amounts that are expected to be returned to customers in the rate-setting process in a period different from the period in which the amounts would be recorded by an unregulated enterprise. Accordingly, the Duke Energy Registrants record assets and liabilities that result from the regulated ratemaking process that would not be recorded under GAAP for nonregulated entities. Regulatory assets and liabilities are amortized consistent with the treatment of the related cost in the ratemaking process. Management continually assesses whether regulatory assets are probable of future recovery by considering factors such as applicable regulatory changes, recent rate orders applicable to other regulated entities and the status of any pending or potential deregulation legislation. Additionally, management continually assesses whether any regulatory liabilities have been incurred. Based on this continual assessment, management believes the existing regulatory assets are probable of recovery and that no regulatory liabilities, other than those recorded, have been incurred. These regulatory assets and liabilities are classified in the Consolidated Balance Sheets as Regulatory assets and Other in Current Assets and as Regulatory liabilities and Other in Current Liabilities, respectively. The Duke Energy Registrants periodically evaluate the applicability of regulatory accounting treatment by considering factors such as regulatory changes and the impact of competition. If cost-based regulation ends or competition increases, the Duke Energy Registrants may have to reduce their asset balances to reflect a market basis less than cost and write-off the associated regulatory assets and liabilities. If it becomes probable that part of the cost of a plant under construction or a recently completed plant will be disallowed for ratemaking purposes and a reasonable estimate of the amount of the disallowance can be made, that amount is recognized as a loss. In November 2011, in conjunction with the PUCO's approval of its new Electric Security Plan (ESP), Duke Energy Ohio ceased applying regulatory accounting treatment to generation operations within its Commercial Power segment. For further information, see Note 4.
Energy Purchases, Fuel Costs And Fuel Cost Deferrals	Energy Purchases, Fuel Costs and Fuel Cost Deferrals. The Duke Energy Registrants utilize cost-tracking mechanisms, commonly referred to as a fuel adjustment clause, to recover the retail portion of fuel and purchased power. The Duke Energy Registrants defer the related cost through Fuel used in electric generation and purchased power — regulated on the Consolidated Statement of Operations, unless a regulatory requirement exists for deferral through Operating Revenues. Fuel used in electric generation and purchased power — regulated includes fuel, purchased power and recoverable costs that are deferred through fuel clauses established by the Subsidiary Registrants' regulators. These clauses allow the Subsidiary Registrants to recover fuel costs, fuel-related costs and portions of purchased power costs through surcharges on customer rates. The Subsidiary Registrants record any under-recovery or over-recovery resulting from the differences between estimated and actual costs as a regulatory asset or regulatory liability until billed or refunded to customers, at which point the differences are adjusted through revenues. Indiana law limits the amount of fuel costs that Duke Energy Indiana can recover to an amount that will not result in earning a return in excess of that allowed by the IURC. As discussed in Note 4, beginning January 1, 2012, Duke Energy Ohio procures energy for its retail customers through a third-party auction. Purchases of energy through the auction process are a pass-through of costs for Duke Energy Ohio, with no affect on earnings. Subsequent to December 31, 2011, Duke Energy Ohio's generation assets are no longer dedicated to retail customers and, accordingly, Duke Energy Ohio can no longer recover their generation assets' energy purchases and fuel costs from regulated customers.
Cash and Cash Equivalents	Cash and Cash Equivalents. All highly liquid investments with maturities of three months or less at the date of acquisition are considered cash equivalents. At December 31, 2012, Duke Energy had cash and cash equivalents of $1,424 million, of which $731 million is held in foreign jurisdictions and is forecasted to be used to fund international operations and investments.
Restricted Cash	Restricted Cash. The Duke Energy Registrants have restricted cash related primarily to collateral assets, escrow deposits, and restricted cash of VIEs. Restricted cash balances are reflected in Other within Current Assets and in Other within Investments and Other Assets on the Consolidated Balance Sheets.
Inventory	Inventory. Inventory is comprised of amounts presented in the tables below and is recorded primarily using the average cost method. Inventory related to the Duke Energy Registrants' regulated operations is valued at historical cost consistent with ratemaking treatment. Materials and supplies are recorded as inventory when purchased and subsequently charged to expense or capitalized to property, plant and equipment when installed. Reserves are established for excess and obsolete inventory. Inventory related to the Duke Energy Registrants' nonregulated operations is valued at the lower of cost or market. The following tables present the Duke Energy Registrants' inventory.
Investments In Debt And Equity Securities	Investments in Debt and Equity Securities. The Duke Energy Registrants classify investments into two categories — trading and available-for-sale. Trading securities are reported at fair value in the Consolidated Balance Sheets with net realized and unrealized gains and losses included in earnings each period. Available-for-sale securities are also reported at fair value on the Consolidated Balance Sheets with unrealized gains and losses included in Accumulated Other Comprehensive Income (AOCI) or as a regulatory asset or liability, unless it is determined that the carrying value of an investment is other-than-temporarily impaired. Other-than-temporary impairments related to equity securities and the credit loss portion of debt securities are included in earnings, unless deferred in accordance with regulatory accounting treatment. Investments in debt and equity securities are classified as either short-term investments or long-term investments based on management's intent and ability to sell these securities, taking into consideration illiquidity factors in the current markets with respect to certain investments that have historically provided for a high degree of liquidity, such as investments in auction rate debt securities. See Note 17 for further information on the investments in debt and equity securities, including investments held in the nuclear decommissioning trust funds (NDTF).
Goodwill	Goodwill. Duke Energy and Duke Energy Ohio perform annual goodwill impairment tests as of August 31 each year and update these tests between annual tests if events or circumstances occur that would more likely than not reduce the fair value of a reporting unit below its carrying value. In 2012, Progress Energy changed its goodwill impairment testing date from October 31 to August 31. The change in the goodwill impairment test date is preferable as it better aligns the annual goodwill impairment testing procedures with the testing procedures of Duke Energy. The change in accounting principle did not accelerate, delay, avoid, or cause a goodwill impairment charge. Neither the change in the goodwill impairment testing date nor the merger resulted in any changes to the Progress Energy reporting units. Due to significant judgments and estimates that are utilized in a goodwill impairment analysis, Progress Energy determined it was impracticable to objectively determine, without the use of hindsight, projected cash flows and related valuation estimates as of each August 31, for periods prior to August 31, 2012. As such, the change in the annual goodwill impairment testing date was prospectively applied from August 31, 2012. Duke Energy, Progress Energy and Duke Energy Ohio perform the annual review for goodwill impairment at the reporting unit level, which Duke Energy and Progress Energy have determined to be an operating segment or one level below and which Duke Energy Ohio has determined to be an operating segment. The annual goodwill impairment test may first consider qualitative factors to determine whether it is more likely than not (i.e. greater than 50 percent chance) that the fair value of a reporting unit is less than its book value. This is sometimes referred to as “step zero” and is an optional step in the annual goodwill impairment analysis (see further discussion as discussed in “New Accounting Standards” below). If the results of qualitative assessments indicate that the fair value of a reporting unit is more likely than not less than the carrying value of the reporting unit, the two-step impairment test is required. Step one of the impairment test involves comparing the fair values of reporting units with their carrying values, including goodwill. If the carrying amount is less than fair value in step one, further testing of goodwill is not performed. If the carrying amount of a reporting unit exceeds the reporting unit's fair value, step two must be performed to determine the amount, if any, of the goodwill impairment loss. Step two of the goodwill impairment test involves comparing the implied fair value of the reporting unit's goodwill against the carrying value of the goodwill. Under step two, determining the implied fair value of goodwill requires the valuation of a reporting unit's identifiable tangible and intangible assets and liabilities as if the reporting unit had been acquired in a business combination on the testing date. The difference between the fair value of the entire reporting unit as determined in step one and the net fair value of all identifiable assets and liabilities represents the implied fair value of goodwill. The goodwill impairment charge, if any, would be the excess of the carrying amount of goodwill over the implied fair value of goodwill upon the completion of step two. As a result of the Progress Energy merger, Duke Energy, Progress Energy and Duke Energy Ohio performed step one of the goodwill impairment test as of August 31, 2012, and concluded the fair value of the reporting units exceeded their respective carrying values, and thus, did not record any impairment charges. In 2011, Duke Energy and Duke Energy Ohio performed the qualitative assessments under step zero and concluded that it was more likely than not the fair value of each reporting unit exceeded its carrying value. In 2011, Progress Energy performed step one of the goodwill impairment test, which indicated the carrying amounts of goodwill were not impaired. In 2010, Duke Energy, Progress Energy and Duke Energy Ohio used the two-step process to test goodwill for impairment, which resulted in impairments recorded by Duke Energy and Duke Energy Ohio. See Note 12 for further information.
Long-Lived Asset Impairments	Long-Lived Asset Impairments. The Duke Energy Registrants evaluate whether long-lived assets, excluding goodwill, have been impaired when circumstances indicate the carrying value of those assets may not be recoverable. For such long-lived assets, an impairment exists when its carrying value exceeds the sum of estimates of the undiscounted cash flows expected to result from the use and eventual disposition of the asset. When alternative courses of action to recover the carrying amount of a long-lived asset are under consideration, a probability-weighted approach is used for developing estimates of future undiscounted cash flows. If the carrying value of the long-lived asset is not recoverable based on these estimated future undiscounted cash flows, the impairment loss is measured as the excess of the carrying value of the asset over its fair value, such that the asset's carrying value is adjusted to its estimated fair value. Management assesses the fair value of long-lived assets using commonly accepted techniques, and may use more than one source. Sources to determine fair value include, but are not limited to, recent third party comparable sales, internally developed discounted cash flow analysis and analysis from outside advisors. Significant changes in market conditions resulting from events such as, among others, changes in commodity prices or the condition of an asset, or a change in management's intent to utilize the asset are generally viewed by management as triggering events to re-assess the cash flows related to the long-lived assets. See Note 12 for further information.
Property, Plant and Equipment	Property, Plant and Equipment. Property, plant and equipment are stated at the lower of historical cost less accumulated depreciation or fair value, if impaired. The Duke Energy Registrants capitalize all construction-related direct labor and material costs, as well as indirect construction costs. Indirect costs include general engineering, taxes and the allowance for funds used during construction (AFUDC). See “AFUDC and Interest Capitalized,” below for additional information. The cost of renewals and betterments that extend the useful life of property, plant and equipment are also capitalized. The cost of repairs, replacements and major maintenance projects, which do not extend the useful life or increase the expected output of the asset, are expensed as incurred. Depreciation is generally computed over the estimated useful life of the asset using the composite straight-line method. For regulated operations, depreciation studies are conducted periodically to update the composite rates and are approved by the various state commissions. The composite weighted-average depreciation rates, excluding nuclear fuel, for each of the Duke Energy Registrants are included in the following table: When the Duke Energy Registrants retire regulated property, plant and equipment under what is considered a normal retirement, the original cost plus the cost of retirement, less salvage value, is charged to accumulated depreciation, consistent with regulated rate-making practices. When it becomes probable that a regulated generation asset will be retired substantially in advance of its original expected useful life or is abandoned, the cost of the asset and the corresponding accumulated depreciation is removed from Cost and Accumulated depreciation and amortization within Property, Plant and Equipment on the Consolidated Balance Sheets and a separate asset is recognized. If the plant is still in operation, the amount is classified as Generation facilities to be retired, net on the Consolidated Balance Sheets. If the plant is no longer operating, then a regulatory asset is recognized. The carrying value of the asset is based on historical cost if the Duke Energy Registrants are allowed to recover the remaining net book value and a full return on the asset. If the Duke Energy Registrants do not expect to recover the full remaining cost and a full return, the carrying value of the asset is based on the lower of cost or the present value of the future revenues expected to be provided to recover the allowable costs discounted at the Duke Energy Registrants' incremental borrowing rate. An impairment is recognized if the net book value of the asset exceeds the present value of the future revenues to be recovered in rates. When the Duke Energy Registrants sell entire regulated operating units, or retire or sell nonregulated properties, the original cost is removed from property and the related accumulated depreciation and amortization balances are reduced. Any gain or loss is recorded in earnings, unless otherwise required by the applicable regulatory body. See Note 10 for further information on the components and estimated useful lives of Duke Energy's property, plant and equipment.
Nuclear Fuel	Nuclear Fuel. Nuclear fuel is classified as Property, Plant and Equipment in the Consolidated Balance Sheets. Nuclear fuel in the front-end fuel processing phase is considered work in progress and not amortized until placed in service. Amortization of nuclear fuel is included within Fuel used in electric generation and purchased power-regulated in the Consolidated Statements of Operations. The amortization is recorded using the units-of-production method.
AFUDC And Interest Capitalized	AFUDC and Interest Capitalized. In accordance with applicable regulatory accounting guidance, the Duke Energy Registrants record AFUDC, which represents the estimated debt and equity costs of capital funds necessary to finance the construction of new regulated facilities. The equity component of AFUDC is a non-cash amount within the Consolidated Statements of Operations. AFUDC is capitalized as a component of the cost of property, plant and equipment, with an offsetting credit to Other income and expenses, net on the Consolidated Statements of Operations for the equity component and as an offset to Interest Expense on the Consolidated Statements of Operations for the debt component. After construction is completed, the Duke Energy Registrants are permitted to recover these costs through inclusion in the rate base and the corresponding depreciation expense or nuclear fuel expense. AFUDC equity is a permanent difference item for income tax purposes, thus reducing the Duke Energy Registrants' effective tax rate during the construction phase in which AFUDC equity is being recorded. The effective tax rate is subsequently increased in future periods when the completed property, plant and equipment are placed in service and depreciation of the AFUDC equity commences. See Note 24 for information related to the impacts of AFUDC equity on the Duke Energy Registrants' effective tax rate. For nonregulated operations, interest is capitalized during the construction phase in accordance with the applicable accounting guidance.
Asset Retirement Obligations	Asset Retirement Obligations. The Duke Energy Registrants recognize asset retirement obligations for legal obligations associated with the retirement of long-lived assets that result from the acquisition, construction, development and/or normal use of the asset, and for conditional asset retirement obligations. The term conditional asset retirement obligation refers to a legal obligation to perform an asset retirement activity in which the timing and (or) method of settlement are conditional on a future event that may or may not be within the control of the entity. The obligation to perform the asset retirement activity is unconditional even though uncertainty exists about the timing and (or) method of settlement. Thus, the timing and (or) method of settlement may be conditional on a future event. When recording an asset retirement obligation, the present value of the projected liability is recognized in the period in which it is incurred, if a reasonable estimate of fair value can be made. The liability is then accreted over time by applying an interest method of allocation to the liability. Substantially all accretion is related to regulated operations and is deferred pursuant to regulatory accounting. The present value of the liability is added to the carrying amount of the associated asset and this additional carrying amount is depreciated over the remaining life of the asset. The present value of the initial obligation and subsequent updates are based on discounted cash flows, which include estimates regarding the timing of future cash flows, the selection of discount rates and cost escalation rates, among other factors. These underlying assumptions and estimates are made as of a point in time and are subject to change. The obligations for nuclear decommissioning are based on site-specific cost studies. Duke Energy Carolinas and Progress Energy Carolinas assume prompt dismantlement of the nuclear facilities, which reflects dismantling the site after operations are ceased. Progress Energy Florida assumes the nuclear facility will be placed into a safe storage configuration until the eventual dismantling of the site begins in approximately 40-60 years. The nuclear decommissioning asset retirement obligation also assumes Duke Energy Carolinas, Progress Energy Carolinas and Progress Energy Florida will store spent fuel on site until such time that it can be transferred to a U.S. Department of Energy (DOE) facility. See Note 9 for further information.
Unbilled Revenue	Revenue Recognition and Unbilled Revenue. Revenues on sales of electricity and gas are recognized when either the service is provided or the product is delivered. Unbilled retail revenues are estimated by applying average revenue per kilowatt-hour (kWh) or per thousand cubic feet (Mcf) for all customer classes to the number of estimated kWh or Mcf delivered but not billed. Unbilled wholesale energy revenues are calculated by applying the contractual rate per megawatt-hour (MWh) to the number of estimated MWh delivered but not yet billed. Unbilled wholesale demand revenues are calculated by applying the contractual rate per megawatt (MW) to the MW volume delivered but not yet billed. The amount of unbilled revenues can vary significantly from period to period as a result of numerous factors, including seasonality, weather, customer usage patterns and customer mix. The Duke Energy Registrants had unbilled revenues within Receivables and within Restricted receivables of variable interest entities on their respective Consolidated Balance Sheets as shown in the table below.
Accounting For Risk Management, Hedging Activities And Financial Instruments	Accounting for Risk Management, Hedging Activities and Financial Instruments. The Duke Energy Registrants may use a number of different derivative and non-derivative instruments in connection with their commodity price, interest rate and foreign currency risk management activities, including swaps, futures, forwards and options. All derivative instruments except those that qualify for the normal purchase/normal sale (NPNS) exception within the accounting guidance for derivatives are recorded on the Consolidated Balance Sheets at their fair value. The effective portion of the change in the fair value of derivative instruments designated as cash flow hedges is recorded in AOCI. The effective portion of the change in the fair value of a fair value hedge is offset in net income by changes in the hedged item. The Duke Energy Registrants may designate qualifying derivative instruments as either cash flow hedges or fair value hedges, while others either have not been designated as hedges or do not qualify as a hedge (hereinafter referred to as undesignated contracts). For all contracts accounted for as a hedge, the Duke Energy Registrants prepare formal documentation of the hedge in accordance with the accounting guidance for derivatives. In addition, at inception and at least every three months thereafter, the Duke Energy Registrants formally assess whether the hedge contract is highly effective in offsetting changes in cash flows or fair values of hedged items. The Duke Energy Registrants document hedging activity by transaction type and risk management strategy. See Note 15 for further information.
Captive Insurance Reserves	Captive Insurance Reserves. Duke Energy has captive insurance subsidiaries that provide coverage, on an indemnity basis, to the Subsidiary Registrants as well as certain third parties, on a limited basis, for various business risks and losses, such as property, business interruption, workers' compensation and general liability. Liabilities include provisions for estimated losses incurred but not yet reported (IBNR), as well as provisions for known claims which have been estimated on a claims-incurred basis. IBNR reserve estimates involve the use of assumptions and are primarily based upon historical loss experience, industry data and other actuarial assumptions. Reserve estimates are adjusted in future periods as actual losses differ from historical experience. Duke Energy, through its captive insurance entities, also has reinsurance coverage with third parties, which provides reimbursement for certain losses above a per occurrence and/or aggregate retention. Duke Energy recognizes a reinsurance receivable for recovery of incurred losses under its captive's reinsurance coverage once realization of the receivable is deemed probable.
Unamortized Debt Premium, Discount And Expense	Unamortized Debt Premium, Discount and Expense. Premiums, discounts and expenses incurred with the issuance of outstanding long-term debt are amortized over the terms of the debt issues. Any call premiums or unamortized expenses associated with refinancing higher-cost debt obligations used to finance regulated assets and operations are amortized consistent with regulatory treatment of those items, where appropriate. The amortization expense is recorded as a component of Interest Expense in the Consolidated Statements of Operations and is reflected as Depreciation, amortization and accretion within Net cash provided by operating activities on the Consolidated Statements of Cash Flows.
Loss Contingencies And Environmental Liabilities	Loss Contingencies and Environmental Liabilities. The Duke Energy Registrants are involved in certain legal and environmental matters that arise in the normal course of business. Contingent losses are recorded when it is determined that it is probable that a loss has occurred and the amount of the loss can be reasonably estimated. When a range of the probable loss exists and no amount within the range is a better estimate than any other amount, the Duke Energy Registrants record a loss contingency at the minimum amount in the range. Unless otherwise required by GAAP, legal fees are expensed as incurred. Environmental liabilities are recorded on an undiscounted basis when the necessity for environmental remediation becomes probable and the costs can be reasonably estimated, or when other potential environmental liabilities are reasonably estimable and probable. The Duke Energy Registrants expense environmental expenditures related to conditions caused by past operations that do not generate current or future revenues. Certain environmental expenses receive regulatory accounting treatment, under which the expenses are recorded as regulatory assets. Environmental expenditures related to operations that generate current or future revenues are expensed or capitalized, as appropriate. See Note 5 for further information.
Pension And Other Post-Retirement Benefit Plans	Pension and Other Post-Retirement Benefit Plans. Duke Energy maintains qualified, non-qualified and other post-retirement benefit plans. Eligible employees of the Subsidiary Registrants participate in the respective Duke Energy or Progress Energy qualified, non-qualified and other post-retirement benefit plans and are allocated their proportionate share of benefit costs. See Note 23 for information related to Duke Energy's benefit plans, including certain accounting policies associated with these plans.
Severance And Special Termination Benefits	Severance and Special Termination Benefits. Duke Energy has an ongoing severance plan under which, in general, the longer a terminated employee worked prior to termination the greater the amount of severance benefits. The Duke Energy Registrants record a liability for involuntary severance once an involuntary severance plan is committed to by management, or sooner, if involuntary severances are probable and the related severance benefits can be reasonably estimated. For involuntary severance benefits that are incremental to its ongoing severance plan benefits, Duke Energy measures the obligation and records the expense at its fair value at the communication date if there are no future service requirements, or, if future service is required to receive the termination benefit, ratably over the service period. From time to time, Duke Energy offers special termination benefits under voluntary severance programs. Special termination benefits are measured upon employee acceptance and recorded immediately absent a significant retention period. If a significant retention period exists, the cost of the special termination benefits are recorded ratably over the remaining service periods of the affected employees. Employee acceptance of voluntary severance benefits is determined by management based on the facts and circumstances of the special termination benefits being offered. See Note 21 for further information.
Guarantees	Guarantees. Upon issuance or modification of a guarantee, the Duke Energy Registrants recognize a liability at the time of issuance or material modification for the estimated fair value of the obligation it assumes under that guarantee, if any. Fair value is estimated using a probability-weighted approach. The Duke Energy Registrants reduce the obligation over the term of the guarantee or related contract in a systematic and rational method as risk is reduced under the obligation. Any additional contingent loss for guarantee contracts subsequent to the initial recognition of a liability in accordance with applicable accounting guidance is accounted for and recognized at the time a loss is probable and the amount of the loss can be reasonably estimated. The Duke Energy Registrants have entered into various indemnification agreements related to purchase and sale agreements and other types of contractual agreements with vendors and other third parties. These agreements typically cover environmental, tax, litigation and other matters, as well as breaches of representations, warranties and covenants. Typically, claims may be made by third parties for various periods of time, depending on the nature of the claim. Potential exposure under these indemnification agreements can range from a specified to an unlimited dollar amount, depending on the nature of the claim and the particular transaction. See Note 7 for further information.
Stock-based Compensation	Stock-Based Compensation. Stock-based compensation represents the cost related to stock-based awards granted to employees. Duke Energy recognizes stock-based compensation based upon the estimated fair value of the awards, net of estimated forfeitures. The recognition period for these costs begin at either the applicable service inception date or grant date and continues throughout the requisite service period, or for certain share-based awards until the employee becomes retirement eligible, if earlier. Share-based awards, including stock options, but not performance shares, granted to employees that are already retirement eligible are deemed to have vested immediately upon issuance, and, therefore, compensation cost for those awards is recognized on the date such awards are granted. See Note 22 for further information.
Accounting For Purchases And Sales Of Emission Allowances	Accounting For Purchases and Sales of Emission Allowances. Emission allowances are issued by the Environmental Protection Agency (EPA) at zero cost and permit the holder of the allowance to emit certain gaseous by-products of fossil fuel combustion, including sulfur dioxide (SO2) and nitrogen oxide (NOx). Allowances may also be bought and sold via third-party transactions. Allowances allocated to or acquired by the Duke Energy Registrants are held primarily for consumption. Emission allowances at cost are included in Intangibles, net on the Consolidated Balance Sheets and the Duke Energy Registrants recognize expense as the allowances are consumed or sold. Gains or losses on sales of emission allowances by regulated businesses that do not provide for direct recovery through a cost-tracking mechanism and by nonregulated businesses are presented in Gains on Sales of Other Assets and Other, net, in the Consolidated Statements of Operations. For regulated businesses that provide for direct recovery of emission allowances, any gain or loss on sales of recoverable emission allowances are included in the rate structure of the regulated entity and are deferred as a regulatory asset or liability. Future rates charged to retail customers are impacted by any gain or loss on sales of recoverable emission allowances. Purchases and sales of emission allowances are presented gross as investing activities on the Consolidated Statements of Cash Flows. See Note 12 for discussion regarding the impairment of the carrying value of certain emission allowances in 2011.
Income Taxes	Income Taxes. Duke Energy and its subsidiaries file a consolidated federal income tax return and other state and foreign jurisdictional returns as required. Deferred income taxes have been provided for temporary differences between the GAAP and tax carrying amounts of assets and liabilities. These differences create taxable or tax-deductible amounts for future periods. Investment tax credits (ITC) associated with regulated operations are deferred and are amortized as a reduction of income tax expense over the estimated useful lives of the related properties. The Subsidiary Registrants entered into a tax sharing agreement with Duke Energy, where the separate return method is used to allocate tax expenses and benefits to the subsidiaries whose investments or results of operations provide these tax expenses or benefits. The accounting for income taxes essentially represents the income taxes that the Subsidiary Registrants would incur if the Subsidiary Registrants were a separate company filing its own federal tax return as a C-Corporation. The Duke Energy Registrants record unrecognized tax benefits for positions taken or expected to be taken on tax returns, including the decision to exclude certain income or transactions from a return, when a more-likely-than-not threshold is met for a tax position and management believes that the position will be sustained upon examination by the taxing authorities. Management evaluates each position based solely on the technical merits and facts and circumstances of the position, assuming the position will be examined by a taxing authority having full knowledge of all relevant information. The Duke Energy Registrants record the largest amount of the unrecognized tax benefit that is greater than 50% likely of being realized upon settlement or effective settlement. Management considers a tax position effectively settled for the purpose of recognizing previously unrecognized tax benefits when the following conditions exist: (i) the taxing authority has completed its examination procedures, including all appeals and administrative reviews that the taxing authority is required and expected to perform for the tax positions, (ii) the Duke Energy Registrants do not intend to appeal or litigate any aspect of the tax position included in the completed examination, and (iii) it is remote that the taxing authority would examine or reexamine any aspect of the tax position. Deferred taxes are not provided on translation gains and losses where Duke Energy expects earnings of a foreign operation to be indefinitely reinvested. The Duke Energy Registrants record tax-related interest expense in Interest Expense and interest income and penalties in Other Income and Expenses, net, in the Consolidated Statements of Operations. See Note 24 for further information.
Excise Taxes	Excise Taxes. Certain excise taxes levied by state or local governments are collected by the Duke Energy Registrants from their customers. These taxes, which are required to be paid regardless of the Duke Energy Registrants' ability to collect from the customer, are accounted for on a gross basis. When the Duke Energy Registrants act as an agent, and the tax is not required to be remitted if it is not collected from the customer, the taxes are accounted for on a net basis. The Duke Energy Registrants' excise taxes accounted for on a gross basis and recorded as operating revenues in the Consolidated Statements of Operations were as follows:
Foreign Currency Transaction	Foreign Currency Translation. The local currencies of Duke Energy's foreign operations have been determined to be their functional currencies, except for certain foreign operations whose functional currency has been determined to be the U.S. Dollar, based on an assessment of the economic circumstances of the foreign operation. Assets and liabilities of foreign operations, except for those whose functional currency is the U.S. Dollar, are translated into U.S. Dollars at the exchange rates in effect at period end. Translation adjustments resulting from fluctuations in exchange rates are included as a separate component of AOCI. Revenue and expense accounts of these operations are translated at average exchange rates prevailing during the year. Gains and losses arising from balances and transactions denominated in currencies other than the functional currency are included in the results of operations in the period in which they occur.
Dividend Restrictions And Unappropriated Retained Earnings	Dividend Restrictions and Unappropriated Retained Earnings. Duke Energy does not have any legal, regulatory or other restrictions on paying common stock dividends to shareholders. However, as further described in Note 4, due to conditions established by regulators at the time of the Duke Energy/Cinergy merger in April 2006 and the Duke Energy/Progress Energy merger in 2012, certain wholly owned subsidiaries, including Duke Energy Carolinas, Progress Energy Carolinas, Duke Energy Ohio and Duke Energy Indiana, have restrictions on paying dividends or otherwise advancing funds to Duke Energy. At December 31, 2012 and 2011, an insignificant amount of Duke Energy's consolidated Retained earnings balance represents undistributed earnings of equity method investments.
New Accounting Standards [Policy Text Block]	New Accounting Standards. The following new accounting standards were adopted by the Duke Energy Registrants during the year ended December 31, 2012, and the impact of such adoption, if applicable, has been presented in the accompanying Consolidated Financial Statements: Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC) 220 — Comprehensive Income. In June 2011, the FASB amended the existing requirements for presenting comprehensive income in financial statements primarily to increase the prominence of items reported in other comprehensive income (OCI) and to facilitate the convergence of U.S. GAAP and International Financial Reporting Standards (IFRS). Specifically, the revised guidance eliminates the option previously provided to present components of OCI as part of the statement of changes in stockholders' equity. Accordingly, all non-owner changes in stockholders' equity are required to be presented either in a single continuous statement of comprehensive income or in two separate but consecutive financial statements. For the Duke Energy Registrants, this revised guidance was effective on a retrospective basis for interim and annual periods beginning January 1, 2012. The adoption of this standard changed the presentation of the Duke Energy Registrants' financial statements but did not affect the calculation of net income, comprehensive income or earnings per share. ASC 820 — Fair Value Measurements and Disclosures. In May 2011, the FASB amended existing requirements for measuring fair value and for disclosing information about fair value measurements. This revised guidance results in a consistent definition of fair value, as well as common requirements for measurement and disclosure of fair value information between U.S. GAAP and IFRS. In addition, the amendments set forth enhanced disclosure requirements with respect to recurring Level 3 measurements, nonfinancial assets measured or disclosed at fair value, transfers between levels in the fair value hierarchy, and assets and liabilities disclosed but not recorded at fair value. For the Duke Energy Registrants, the revised fair value measurement guidance was effective on a prospective basis for interim and annual periods beginning January 1, 2012. The adoption of this new guidance did not have a significant impact on the Duke Energy Registrants disclosures or their consolidated results of operations, cash flows, or financial position. The following new accounting standards were adopted by Duke Energy during the year ended December 31, 2011, and the impact of such adoption, if applicable has been presented in the accompanying Consolidated Financial Statements: ASC 605 — Revenue Recognition. In October 2009, the FASB issued new revenue recognition accounting guidance in response to practice concerns related to the accounting for revenue arrangements with multiple deliverables. This new accounting guidance primarily applies to all contractual arrangements in which a vendor will perform multiple revenue generating activities and addresses the unit of accounting for arrangements involving multiple deliverables, as well as how arrangement consideration should be allocated to the separate units of accounting. For the Duke Energy Registrants, the new accounting guidance was effective January 1, 2011, and applied on a prospective basis. This new accounting guidance did not have a material impact to the consolidated results of operations, cash flows or financial position of the Duke Energy Registrants. ASC 805 — Business Combinations. In November 2010, the FASB issued new accounting guidance in response to diversity in the interpretation of pro forma information disclosure requirements for business combinations. The new accounting guidance requires an entity to present pro forma financial information as if a business combination occurred at the beginning of the earliest period presented as well as additional disclosures describing the nature and amount of material, nonrecurring pro forma adjustments. This new accounting guidance was effective January 1, 2011, and has been applied to all business combinations consummated after that date. ASC 820 — Fair Value Measurements and Disclosures. In January 2010, the FASB amended existing fair value measurements and disclosures accounting guidance to clarify certain existing disclosure requirements and to require a number of additional disclosures, including amounts and reasons for significant transfers between the three levels of the fair value hierarchy, and presentation of certain information in the reconciliation of recurring Level 3 measurements on a gross basis. For the Duke Energy Registrants, certain portions of this revised accounting guidance were effective on January 1, 2010, with additional disclosures effective for periods beginning January 1, 2011. The adoption of this accounting guidance resulted in additional disclosure in the notes to the consolidated financial statements but did not have an impact on the Duke Energy Registrants' consolidated results of operations, cash flows or financial position. ASC 350 — Intangibles–Goodwill and Other. In September 2011, the FASB amended existing goodwill impairment testing accounting guidance to provide an entity testing goodwill for impairment with the option of performing a qualitative assessment prior to calculating the fair value of a reporting unit in step one of a goodwill impairment test. Under this revised guidance, a qualitative assessment would require an evaluation of economic, industry, and company-specific considerations. If an entity determines, on a basis of such qualitative factors, that the fair value of a reporting unit is more likely than not less than the carrying value of a reporting unit, the two-step impairment test, as required under pre-existing applicable accounting guidance, would be required. Otherwise, no further impairment testing would be required. The revised goodwill impairment testing accounting guidance is effective for the Duke Energy Registrants' annual and interim goodwill impairment tests performed for fiscal years beginning January 1, 2012, with early adoption of this revised guidance permitted for annual and interim goodwill impairment tests performed as of a date before September 15, 2011. Since annual goodwill impairment tests are performed by Duke Energy as of August 31, the Duke Energy Registrants early adopted this revised accounting guidance during the third quarter of 2011 and applied that guidance to their annual goodwill impairment tests for 2011. The following new accounting standards were adopted by Duke Energy during the year ended December 31, 2010, and the impact of such adoption, if applicable has been presented in the accompanying Consolidated Financial Statements: ASC 860 — Transfers and Servicing. In June 2009, the FASB issued revised accounting guidance for transfers and servicing of financial assets and extinguishment of liabilities, to require additional information about transfers of financial assets, including securitization transactions, as well as additional information about an enterprise's continuing exposure to the risks related to transferred financial assets. This revised accounting guidance eliminated the concept of a Qualifying Special Purpose Entity (QSPE) and required those entities which were not subject to consolidation under previous accounting rules to now be assessed for consolidation. In addition, this accounting guidance clarified and amended the derecognition criteria for transfers of financial assets (including transfers of portions of financial assets) and required additional disclosures about a transferor's continuing involvement in transferred financial assets. For Duke Energy, this revised accounting guidance was effective prospectively for transfers of financial assets occurring on or after January 1, 2010, and early adoption of this statement was prohibited. Since 2002, Duke Energy Ohio, Duke Energy Indiana, and Duke Energy Kentucky have sold, on a revolving basis, nearly all of their accounts receivable and related collections through CRC, a bankruptcy-remote QSPE. The securitization transaction was structured to meet the criteria for sale accounting treatment, and, accordingly, Duke Energy did not consolidate CRC, and the transfers were accounted for as sales. Effective with adoption of this revised accounting guidance and ASC 810-Consolidation, as discussed below, the accounting treatment and/or financial statement presentation of Duke Energy's accounts receivable securitization programs was impacted as Duke Energy began consolidating CRC effective January 1, 2010. Duke Energy Ohio's and Duke Energy Indiana's sales of accounts receivable and related financial statement presentation were not impacted by the adoption of ASC 860. ASC 810 — Consolidations. In June 2009, the FASB amended existing consolidation accounting guidance to eliminate the exemption from consolidation for QSPEs, and clarified, but did not significantly change, the criteria for determining whether an entity meets the definition of a VIE. This revised accounting guidance also required an enterprise to qualitatively assess the determination of the primary beneficiary of a VIE based on whether that enterprise has both the power to direct the activities that most significantly impact the economic performance of a VIE and the obligation to absorb losses or the right to receive benefits of a VIE that could potentially be significant to a VIE. In addition, this revised accounting guidance modified existing accounting guidance to require an ongoing evaluation of a VIE's primary beneficiary and amended the types of events that trigger a reassessment of whether an entity is a VIE. Furthermore, this accounting guidance required enterprises to provide additional disclosures about their involvement with VIEs and any significant changes in their risk exposure due to that involvement. For the Duke Energy Registrants, this accounting guidance was effective beginning on January 1, 2010, and is applicable to all entities in which Duke Energy is involved, including entities previously subject to existing accounting guidance for VIEs, as well as any QSPEs that existed as of the effective date. Effective with adoption of this revised accounting guidance, the accounting treatment and/or financial statement presentation of Duke Energy's accounts receivable securitization programs were impacted as Duke Energy began consolidating CRC effective January 1, 2010. Duke Energy Ohio's and Duke Energy Indiana's sales of accounts receivable and related financial statement presentation were not impacted by the adoption of ASC 810. This revised accounting guidance did not have a significant impact on any of the Duke Energy Registrants' other interests in VIEs. ASC 820 — Fair Value Measurements and Disclosures. In January 2010, the FASB amended existing fair value measurements and disclosures accounting guidance to clarify certain existing disclosure requirements and to require a number of additional disclosures, including amounts and reasons for significant transfers between the three levels of the fair value hierarchy, and presentation of certain information in the reconciliation of recurring Level 3 measurements on a gross basis. For the Duke Energy Registrants, certain portions of this revised accounting guidance were effective on January 1, 2010, with additional disclosures effective for periods beginning January 1, 2011. The initial adoption of this accounting guidance resulted in additional disclosure in the notes to the consolidated financial statements but did not have an impact on the Duke Energy Registrants' consolidated results of operations, cash flows or financial position. The following new Accounting Standards Updates (ASU) have been issued, but have not yet been adopted by Duke Energy, as of December 31, 2012. ASC 210 — Balance Sheet. In December 2011, the FASB issued revised accounting guidance to amend the existing disclosure requirements for offsetting financial assets and liabilities to enhance current disclosures, as well as to improve comparability of balance sheets prepared under U.S. GAAP and IFRS. The revised disclosure guidance affects all companies that have financial instruments and derivative instruments that are either offset in the balance sheet (i.e., presented on a net basis) or subject to an enforceable master netting arrangement and/or similar agreement. The revised guidance requires that certain enhanced quantitative and qualitative disclosures be made with respect to a company's netting arrangements and/or rights of setoff associated with its financial instruments and/or derivative instruments including associated collateral. For the Duke Energy Registrants, the revised disclosure guidance is effective on a retrospective basis for interim and annual periods beginning January 1, 2013. Other than additional disclosures, this revised guidance does not impact the Duke Energy Registrants' consolidated results of operations, cash flows or financial position. ASC 220 — Comprehensive Income. In February 2013, the FASB amended the existing requirements for presenting comprehensive income in financial statements to improve the reporting of reclassifications out of AOCI. The amendments in this Update seek to attain that objective by requiring an entity to report the effect of significant reclassifications out of AOCI on the respective line items in net income if the amount being reclassified is required under U.S. GAAP to be reclassified in its entirety to net income. For other amounts that are not required under U.S. GAAP to be reclassified in their entirety to net income in the same reporting period, an entity is required to cross-reference other disclosures required under U.S. GAAP that provide additional detail about those amounts. This would be the case when a portion of the amount reclassified out of AOCI is reclassified to a balance sheet account (for example, inventory) instead of directly to income or expense in the same reporting period. For the Duke Energy Registrants, this revised guidance is effective on a prospective basis for interim and annual periods beginning January 1, 2013. Other than additional disclosures or a change in the presentation on the statement of comprehensive income, this revised guidance does not impact the Duke Energy Registrants' consolidated results of operations, cash flows or financial position.
Progress Energy Carolinas [Member]
Policy Text Block [Line Items]
Organization	Nature of Operations and Basis of Consolidation. Duke Energy Corporation (collectively with its subsidiaries, Duke Energy), is an energy company headquartered in Charlotte, North Carolina. Duke Energy operates in the United States (U.S.) and Latin America primarily through its direct and indirect subsidiaries. Duke Energy's subsidiaries included Duke Energy Carolinas, LLC (Duke Energy Carolinas), Duke Energy Ohio, Inc. (Duke Energy Ohio), which includes Duke Energy Kentucky, Inc. (Duke Energy Kentucky), and Duke Energy Indiana, Inc. (Duke Energy Indiana) prior to the merger with Progress Energy, Inc. (Progress Energy). On July 2, 2012, Duke Energy merged with Progress Energy, with Duke Energy continuing as the surviving corporation, and Progress Energy becoming a subsidiary of Duke Energy. Carolina Power & Light Company d/b/a Progress Energy Carolinas, Inc. (Progress Energy Carolinas) and Florida Power Corporation d/b/a Progress Energy Florida, Inc. (Progress Energy Florida), Progress Energy's regulated utility subsidiaries, are now indirect subsidiaries of Duke Energy. Duke Energy's consolidated financial statements include Progress Energy, Progress Energy Carolinas and Progress Energy Florida activity beginning July 2, 2012. See Note 2 for additional information regarding the merger. When discussing Duke Energy's consolidated financial information, it necessarily includes the results of its six separate subsidiary registrants, Duke Energy Carolinas, Progress Energy, Progress Energy Carolinas, Progress Energy Florida, Duke Energy Ohio and Duke Energy Indiana (collectively referred to as the Subsidiary Registrants), which, along with Duke Energy, are collectively referred to as the Duke Energy Registrants. Progress Energy, Progress Energy Carolinas and Progress Energy Florida (collectively referred to as the Progress Energy Registrants) continue to maintain reporting requirements as SEC registrants. In accordance with SEC guidance, the Progress Energy Registrants did not reflect the impacts of acquisition accounting from the merger with Duke Energy, whereby the adjustments of assets and liabilities to fair value and the resultant goodwill would be shown on the financial statements of the Progress Energy Registrants. These adjustments were recorded by Duke Energy. The information in these combined notes relates to each of the Duke Energy Registrants as noted in the Index to the Combined Notes. However, none of the registrants makes any representation as to information related solely to Duke Energy or the subsidiaries of Duke Energy other than itself. As discussed further in Note 3, Duke Energy operates three reportable business segments: U.S. Franchised Electric and Gas (USFE&G), Commercial Power and International Energy. The remainder of Duke Energy's operations is presented as Other. These Consolidated Financial Statements include, after eliminating intercompany transactions and balances, the accounts of the Duke Energy Registrants and all majority-owned subsidiaries where the respective Duke Energy Registrants have control and those variable interest entities (VIEs) where the respective Duke Energy Registrants are the primary beneficiary. These Consolidated Financial Statements also reflect the Duke Energy Registrants' proportionate share of certain generation and transmission facilities. In January 2012, Duke Energy Ohio completed the sale of its 75% ownership of the Vermillion Generating Station (Vermillion); upon the close, Duke Energy Indiana purchased a 62.5% interest in the station. See Note 2 for further discussion. Duke Energy Carolinas, a wholly owned subsidiary of Duke Energy, is an electric utility company that generates, transmits, distributes and sells electricity in North Carolina and South Carolina. Duke Energy Carolinas is subject to the regulatory provisions of the North Carolina Utilities Commission (NCUC), the Public Service Commission of South Carolina (PSCSC), the U.S. Nuclear Regulatory Commission (NRC) and the Federal Energy Regulatory Commission (FERC). Substantially all of Duke Energy Carolinas' operations are regulated and qualify for regulatory accounting treatment. As discussed further in Note 3, Duke Energy Carolinas' operations include one reportable business segment, Franchised Electric. Progress Energy, a wholly owned subsidiary of Duke Energy, is a holding company headquartered in Raleigh, North Carolina, subject to regulation by the FERC. Progress Energy conducts operations through its wholly owned subsidiaries, Progress Energy Carolinas and Progress Energy Florida. As discussed further in Note 3, Progress Energy's operations include one reportable segment, Franchised Electric. Progress Energy Carolinas, an indirect wholly owned subsidiary of Duke Energy, is a regulated public utility primarily engaged in the generation, transmission, distribution and sale of electricity in portions of North Carolina and South Carolina. Progress Energy Carolinas is subject to the regulatory provisions of the NCUC, the PSCSC, the NRC and the FERC. Substantially all of Progress Energy Carolinas' operations are regulated and qualify for regulatory accounting treatment. As discussed further in Note 3, Progress Energy Carolinas' operations include one reportable segment, Franchised Electric. Progress Energy Florida, an indirect wholly owned subsidiary of Duke Energy, is a regulated public utility primarily engaged in the generation, transmission, distribution and sale of electricity in west central Florida. Progress Energy Florida is subject to the regulatory jurisdiction of the Florida Public Service Commission (FPSC), the NRC and the FERC. Substantially all of Progress Energy Florida's operations are regulated and qualify for regulatory accounting treatment. As discussed further in Note 3, Progress Energy Florida's operations include one reportable segment, Franchised Electric. Duke Energy Ohio, an indirect wholly owned subsidiary of Duke Energy, is a combination electric and gas public utility that provides service in the southwestern portion of Ohio and in northern Kentucky through its wholly owned subsidiary, Duke Energy Kentucky, as well as electric generation in parts of Ohio, Illinois and Pennsylvania. Duke Energy Ohio's principal lines of business include generation, transmission and distribution of electricity, the sale of and/or transportation of natural gas, and energy marketing. Duke Energy Ohio conducts competitive auctions for retail electricity supply in Ohio whereby the energy price is recovered from retail customers. Duke Energy Kentucky's principal lines of business include generation, transmission and distribution of electricity, as well as the sale of and/or transportation of natural gas. References herein to Duke Energy Ohio include Duke Energy Ohio and its subsidiaries, unless otherwise noted. Duke Energy Ohio is subject to the regulatory provisions of the Public Utilities Commission of Ohio (PUCO), the Kentucky Public Service Commission (KPSC) and the FERC. Duke Energy Ohio applies regulatory accounting treatment to substantially all of the operations in its Franchised Electric and Gas operating segment. Through November 2011, Duke Energy Ohio applied regulatory accounting treatment to certain rate riders associated with retail generation of its Commercial Power operating segment. See Note 3 for further information about Duke Energy Ohio's business segments. Duke Energy Indiana, an indirect wholly owned subsidiary of Duke Energy, is an electric utility that provides service in north central, central, and southern Indiana. Its primary line of business is generation, transmission and distribution of electricity. Duke Energy Indiana is subject to the regulatory provisions of the Indiana Utility Regulatory Commission (IURC) and the FERC. Substantially all of Duke Energy Indiana's operations are regulated and qualify for regulatory accounting treatment. As discussed further in Note 3, Duke Energy Indiana's operations include one reportable business segment, Franchised Electric. Certain prior year amounts have been reclassified to conform to current year presentation. In addition, prior year financial statements and footnote disclosures for the Progress Energy Registrants have been reclassified to conform to Duke Energy's presentation.
Use Of Estimates	Use of Estimates. To conform to generally accepted accounting principles (GAAP) in the U.S., management makes estimates and assumptions that affect the amounts reported in the Consolidated Financial Statements and Notes. Although these estimates are based on management's best available information at the time, actual results could differ.
Cost-Based Regulation	Cost-Based Regulation. The Duke Energy Registrants account for their regulated operations in accordance with applicable regulatory accounting guidance. The economic effects of regulation can result in a regulated company recording assets for costs that have been or are expected to be approved for recovery from customers in a future period or recording liabilities for amounts that are expected to be returned to customers in the rate-setting process in a period different from the period in which the amounts would be recorded by an unregulated enterprise. Accordingly, the Duke Energy Registrants record assets and liabilities that result from the regulated ratemaking process that would not be recorded under GAAP for nonregulated entities. Regulatory assets and liabilities are amortized consistent with the treatment of the related cost in the ratemaking process. Management continually assesses whether regulatory assets are probable of future recovery by considering factors such as applicable regulatory changes, recent rate orders applicable to other regulated entities and the status of any pending or potential deregulation legislation. Additionally, management continually assesses whether any regulatory liabilities have been incurred. Based on this continual assessment, management believes the existing regulatory assets are probable of recovery and that no regulatory liabilities, other than those recorded, have been incurred. These regulatory assets and liabilities are classified in the Consolidated Balance Sheets as Regulatory assets and Other in Current Assets and as Regulatory liabilities and Other in Current Liabilities, respectively. The Duke Energy Registrants periodically evaluate the applicability of regulatory accounting treatment by considering factors such as regulatory changes and the impact of competition. If cost-based regulation ends or competition increases, the Duke Energy Registrants may have to reduce their asset balances to reflect a market basis less than cost and write-off the associated regulatory assets and liabilities. If it becomes probable that part of the cost of a plant under construction or a recently completed plant will be disallowed for ratemaking purposes and a reasonable estimate of the amount of the disallowance can be made, that amount is recognized as a loss. In November 2011, in conjunction with the PUCO's approval of its new Electric Security Plan (ESP), Duke Energy Ohio ceased applying regulatory accounting treatment to generation operations within its Commercial Power segment. For further information, see Note 4.
Energy Purchases, Fuel Costs And Fuel Cost Deferrals	Energy Purchases, Fuel Costs and Fuel Cost Deferrals. The Duke Energy Registrants utilize cost-tracking mechanisms, commonly referred to as a fuel adjustment clause, to recover the retail portion of fuel and purchased power. The Duke Energy Registrants defer the related cost through Fuel used in electric generation and purchased power — regulated on the Consolidated Statement of Operations, unless a regulatory requirement exists for deferral through Operating Revenues. Fuel used in electric generation and purchased power — regulated includes fuel, purchased power and recoverable costs that are deferred through fuel clauses established by the Subsidiary Registrants' regulators. These clauses allow the Subsidiary Registrants to recover fuel costs, fuel-related costs and portions of purchased power costs through surcharges on customer rates. The Subsidiary Registrants record any under-recovery or over-recovery resulting from the differences between estimated and actual costs as a regulatory asset or regulatory liability until billed or refunded to customers, at which point the differences are adjusted through revenues. Indiana law limits the amount of fuel costs that Duke Energy Indiana can recover to an amount that will not result in earning a return in excess of that allowed by the IURC. As discussed in Note 4, beginning January 1, 2012, Duke Energy Ohio procures energy for its retail customers through a third-party auction. Purchases of energy through the auction process are a pass-through of costs for Duke Energy Ohio, with no affect on earnings. Subsequent to December 31, 2011, Duke Energy Ohio's generation assets are no longer dedicated to retail customers and, accordingly, Duke Energy Ohio can no longer recover their generation assets' energy purchases and fuel costs from regulated customers.
Cash and Cash Equivalents	Cash and Cash Equivalents. All highly liquid investments with maturities of three months or less at the date of acquisition are considered cash equivalents. At December 31, 2012, Duke Energy had cash and cash equivalents of $1,424 million, of which $731 million is held in foreign jurisdictions and is forecasted to be used to fund international operations and investments.
Restricted Cash	Restricted Cash. The Duke Energy Registrants have restricted cash related primarily to collateral assets, escrow deposits, and restricted cash of VIEs. Restricted cash balances are reflected in Other within Current Assets and in Other within Investments and Other Assets on the Consolidated Balance Sheets.
Inventory	Inventory. Inventory is comprised of amounts presented in the tables below and is recorded primarily using the average cost method. Inventory related to the Duke Energy Registrants' regulated operations is valued at historical cost consistent with ratemaking treatment. Materials and supplies are recorded as inventory when purchased and subsequently charged to expense or capitalized to property, plant and equipment when installed. Reserves are established for excess and obsolete inventory. Inventory related to the Duke Energy Registrants' nonregulated operations is valued at the lower of cost or market. The following tables present the Duke Energy Registrants' inventory.
Investments In Debt And Equity Securities	Investments in Debt and Equity Securities. The Duke Energy Registrants classify investments into two categories — trading and available-for-sale. Trading securities are reported at fair value in the Consolidated Balance Sheets with net realized and unrealized gains and losses included in earnings each period. Available-for-sale securities are also reported at fair value on the Consolidated Balance Sheets with unrealized gains and losses included in Accumulated Other Comprehensive Income (AOCI) or as a regulatory asset or liability, unless it is determined that the carrying value of an investment is other-than-temporarily impaired. Other-than-temporary impairments related to equity securities and the credit loss portion of debt securities are included in earnings, unless deferred in accordance with regulatory accounting treatment. Investments in debt and equity securities are classified as either short-term investments or long-term investments based on management's intent and ability to sell these securities, taking into consideration illiquidity factors in the current markets with respect to certain investments that have historically provided for a high degree of liquidity, such as investments in auction rate debt securities. See Note 17 for further information on the investments in debt and equity securities, including investments held in the nuclear decommissioning trust funds (NDTF).
Long-Lived Asset Impairments	Long-Lived Asset Impairments. The Duke Energy Registrants evaluate whether long-lived assets, excluding goodwill, have been impaired when circumstances indicate the carrying value of those assets may not be recoverable. For such long-lived assets, an impairment exists when its carrying value exceeds the sum of estimates of the undiscounted cash flows expected to result from the use and eventual disposition of the asset. When alternative courses of action to recover the carrying amount of a long-lived asset are under consideration, a probability-weighted approach is used for developing estimates of future undiscounted cash flows. If the carrying value of the long-lived asset is not recoverable based on these estimated future undiscounted cash flows, the impairment loss is measured as the excess of the carrying value of the asset over its fair value, such that the asset's carrying value is adjusted to its estimated fair value. Management assesses the fair value of long-lived assets using commonly accepted techniques, and may use more than one source. Sources to determine fair value include, but are not limited to, recent third party comparable sales, internally developed discounted cash flow analysis and analysis from outside advisors. Significant changes in market conditions resulting from events such as, among others, changes in commodity prices or the condition of an asset, or a change in management's intent to utilize the asset are generally viewed by management as triggering events to re-assess the cash flows related to the long-lived assets. See Note 12 for further information.
Property, Plant and Equipment	Property, Plant and Equipment. Property, plant and equipment are stated at the lower of historical cost less accumulated depreciation or fair value, if impaired. The Duke Energy Registrants capitalize all construction-related direct labor and material costs, as well as indirect construction costs. Indirect costs include general engineering, taxes and the allowance for funds used during construction (AFUDC). See “AFUDC and Interest Capitalized,” below for additional information. The cost of renewals and betterments that extend the useful life of property, plant and equipment are also capitalized. The cost of repairs, replacements and major maintenance projects, which do not extend the useful life or increase the expected output of the asset, are expensed as incurred. Depreciation is generally computed over the estimated useful life of the asset using the composite straight-line method. For regulated operations, depreciation studies are conducted periodically to update the composite rates and are approved by the various state commissions. The composite weighted-average depreciation rates, excluding nuclear fuel, for each of the Duke Energy Registrants are included in the following table: When the Duke Energy Registrants retire regulated property, plant and equipment under what is considered a normal retirement, the original cost plus the cost of retirement, less salvage value, is charged to accumulated depreciation, consistent with regulated rate-making practices. When it becomes probable that a regulated generation asset will be retired substantially in advance of its original expected useful life or is abandoned, the cost of the asset and the corresponding accumulated depreciation is removed from Cost and Accumulated depreciation and amortization within Property, Plant and Equipment on the Consolidated Balance Sheets and a separate asset is recognized. If the plant is still in operation, the amount is classified as Generation facilities to be retired, net on the Consolidated Balance Sheets. If the plant is no longer operating, then a regulatory asset is recognized. The carrying value of the asset is based on historical cost if the Duke Energy Registrants are allowed to recover the remaining net book value and a full return on the asset. If the Duke Energy Registrants do not expect to recover the full remaining cost and a full return, the carrying value of the asset is based on the lower of cost or the present value of the future revenues expected to be provided to recover the allowable costs discounted at the Duke Energy Registrants' incremental borrowing rate. An impairment is recognized if the net book value of the asset exceeds the present value of the future revenues to be recovered in rates. When the Duke Energy Registrants sell entire regulated operating units, or retire or sell nonregulated properties, the original cost is removed from property and the related accumulated depreciation and amortization balances are reduced. Any gain or loss is recorded in earnings, unless otherwise required by the applicable regulatory body. See Note 10 for further information on the components and estimated useful lives of Duke Energy's property, plant and equipment.
Nuclear Fuel	Nuclear Fuel. Nuclear fuel is classified as Property, Plant and Equipment in the Consolidated Balance Sheets. Nuclear fuel in the front-end fuel processing phase is considered work in progress and not amortized until placed in service. Amortization of nuclear fuel is included within Fuel used in electric generation and purchased power-regulated in the Consolidated Statements of Operations. The amortization is recorded using the units-of-production method.
AFUDC And Interest Capitalized	AFUDC and Interest Capitalized. In accordance with applicable regulatory accounting guidance, the Duke Energy Registrants record AFUDC, which represents the estimated debt and equity costs of capital funds necessary to finance the construction of new regulated facilities. The equity component of AFUDC is a non-cash amount within the Consolidated Statements of Operations. AFUDC is capitalized as a component of the cost of property, plant and equipment, with an offsetting credit to Other income and expenses, net on the Consolidated Statements of Operations for the equity component and as an offset to Interest Expense on the Consolidated Statements of Operations for the debt component. After construction is completed, the Duke Energy Registrants are permitted to recover these costs through inclusion in the rate base and the corresponding depreciation expense or nuclear fuel expense. AFUDC equity is a permanent difference item for income tax purposes, thus reducing the Duke Energy Registrants' effective tax rate during the construction phase in which AFUDC equity is being recorded. The effective tax rate is subsequently increased in future periods when the completed property, plant and equipment are placed in service and depreciation of the AFUDC equity commences. See Note 24 for information related to the impacts of AFUDC equity on the Duke Energy Registrants' effective tax rate. For nonregulated operations, interest is capitalized during the construction phase in accordance with the applicable accounting guidance.
Asset Retirement Obligations	Asset Retirement Obligations. The Duke Energy Registrants recognize asset retirement obligations for legal obligations associated with the retirement of long-lived assets that result from the acquisition, construction, development and/or normal use of the asset, and for conditional asset retirement obligations. The term conditional asset retirement obligation refers to a legal obligation to perform an asset retirement activity in which the timing and (or) method of settlement are conditional on a future event that may or may not be within the control of the entity. The obligation to perform the asset retirement activity is unconditional even though uncertainty exists about the timing and (or) method of settlement. Thus, the timing and (or) method of settlement may be conditional on a future event. When recording an asset retirement obligation, the present value of the projected liability is recognized in the period in which it is incurred, if a reasonable estimate of fair value can be made. The liability is then accreted over time by applying an interest method of allocation to the liability. Substantially all accretion is related to regulated operations and is deferred pursuant to regulatory accounting. The present value of the liability is added to the carrying amount of the associated asset and this additional carrying amount is depreciated over the remaining life of the asset. The present value of the initial obligation and subsequent updates are based on discounted cash flows, which include estimates regarding the timing of future cash flows, the selection of discount rates and cost escalation rates, among other factors. These underlying assumptions and estimates are made as of a point in time and are subject to change. The obligations for nuclear decommissioning are based on site-specific cost studies. Duke Energy Carolinas and Progress Energy Carolinas assume prompt dismantlement of the nuclear facilities, which reflects dismantling the site after operations are ceased. Progress Energy Florida assumes the nuclear facility will be placed into a safe storage configuration until the eventual dismantling of the site begins in approximately 40-60 years. The nuclear decommissioning asset retirement obligation also assumes Duke Energy Carolinas, Progress Energy Carolinas and Progress Energy Florida will store spent fuel on site until such time that it can be transferred to a U.S. Department of Energy (DOE) facility. See Note 9 for further information.
Unbilled Revenue	Revenue Recognition and Unbilled Revenue. Revenues on sales of electricity and gas are recognized when either the service is provided or the product is delivered. Unbilled retail revenues are estimated by applying average revenue per kilowatt-hour (kWh) or per thousand cubic feet (Mcf) for all customer classes to the number of estimated kWh or Mcf delivered but not billed. Unbilled wholesale energy revenues are calculated by applying the contractual rate per megawatt-hour (MWh) to the number of estimated MWh delivered but not yet billed. Unbilled wholesale demand revenues are calculated by applying the contractual rate per megawatt (MW) to the MW volume delivered but not yet billed. The amount of unbilled revenues can vary significantly from period to period as a result of numerous factors, including seasonality, weather, customer usage patterns and customer mix. The Duke Energy Registrants had unbilled revenues within Receivables and within Restricted receivables of variable interest entities on their respective Consolidated Balance Sheets as shown in the table below.
Accounting For Risk Management, Hedging Activities And Financial Instruments	Accounting for Risk Management, Hedging Activities and Financial Instruments. The Duke Energy Registrants may use a number of different derivative and non-derivative instruments in connection with their commodity price, interest rate and foreign currency risk management activities, including swaps, futures, forwards and options. All derivative instruments except those that qualify for the normal purchase/normal sale (NPNS) exception within the accounting guidance for derivatives are recorded on the Consolidated Balance Sheets at their fair value. The effective portion of the change in the fair value of derivative instruments designated as cash flow hedges is recorded in AOCI. The effective portion of the change in the fair value of a fair value hedge is offset in net income by changes in the hedged item. The Duke Energy Registrants may designate qualifying derivative instruments as either cash flow hedges or fair value hedges, while others either have not been designated as hedges or do not qualify as a hedge (hereinafter referred to as undesignated contracts). For all contracts accounted for as a hedge, the Duke Energy Registrants prepare formal documentation of the hedge in accordance with the accounting guidance for derivatives. In addition, at inception and at least every three months thereafter, the Duke Energy Registrants formally assess whether the hedge contract is highly effective in offsetting changes in cash flows or fair values of hedged items. The Duke Energy Registrants document hedging activity by transaction type and risk management strategy. See Note 15 for further information.
Captive Insurance Reserves	Captive Insurance Reserves. Duke Energy has captive insurance subsidiaries that provide coverage, on an indemnity basis, to the Subsidiary Registrants as well as certain third parties, on a limited basis, for various business risks and losses, such as property, business interruption, workers' compensation and general liability. Liabilities include provisions for estimated losses incurred but not yet reported (IBNR), as well as provisions for known claims which have been estimated on a claims-incurred basis. IBNR reserve estimates involve the use of assumptions and are primarily based upon historical loss experience, industry data and other actuarial assumptions. Reserve estimates are adjusted in future periods as actual losses differ from historical experience. Duke Energy, through its captive insurance entities, also has reinsurance coverage with third parties, which provides reimbursement for certain losses above a per occurrence and/or aggregate retention. Duke Energy recognizes a reinsurance receivable for recovery of incurred losses under its captive's reinsurance coverage once realization of the receivable is deemed probable.
Unamortized Debt Premium, Discount And Expense	Unamortized Debt Premium, Discount and Expense. Premiums, discounts and expenses incurred with the issuance of outstanding long-term debt are amortized over the terms of the debt issues. Any call premiums or unamortized expenses associated with refinancing higher-cost debt obligations used to finance regulated assets and operations are amortized consistent with regulatory treatment of those items, where appropriate. The amortization expense is recorded as a component of Interest Expense in the Consolidated Statements of Operations and is reflected as Depreciation, amortization and accretion within Net cash provided by operating activities on the Consolidated Statements of Cash Flows.
Loss Contingencies And Environmental Liabilities	Loss Contingencies and Environmental Liabilities. The Duke Energy Registrants are involved in certain legal and environmental matters that arise in the normal course of business. Contingent losses are recorded when it is determined that it is probable that a loss has occurred and the amount of the loss can be reasonably estimated. When a range of the probable loss exists and no amount within the range is a better estimate than any other amount, the Duke Energy Registrants record a loss contingency at the minimum amount in the range. Unless otherwise required by GAAP, legal fees are expensed as incurred. Environmental liabilities are recorded on an undiscounted basis when the necessity for environmental remediation becomes probable and the costs can be reasonably estimated, or when other potential environmental liabilities are reasonably estimable and probable. The Duke Energy Registrants expense environmental expenditures related to conditions caused by past operations that do not generate current or future revenues. Certain environmental expenses receive regulatory accounting treatment, under which the expenses are recorded as regulatory assets. Environmental expenditures related to operations that generate current or future revenues are expensed or capitalized, as appropriate. See Note 5 for further information.
Pension And Other Post-Retirement Benefit Plans	Pension and Other Post-Retirement Benefit Plans. Duke Energy maintains qualified, non-qualified and other post-retirement benefit plans. Eligible employees of the Subsidiary Registrants participate in the respective Duke Energy or Progress Energy qualified, non-qualified and other post-retirement benefit plans and are allocated their proportionate share of benefit costs. See Note 23 for information related to Duke Energy's benefit plans, including certain accounting policies associated with these plans.
Severance And Special Termination Benefits	Severance and Special Termination Benefits. Duke Energy has an ongoing severance plan under which, in general, the longer a terminated employee worked prior to termination the greater the amount of severance benefits. The Duke Energy Registrants record a liability for involuntary severance once an involuntary severance plan is committed to by management, or sooner, if involuntary severances are probable and the related severance benefits can be reasonably estimated. For involuntary severance benefits that are incremental to its ongoing severance plan benefits, Duke Energy measures the obligation and records the expense at its fair value at the communication date if there are no future service requirements, or, if future service is required to receive the termination benefit, ratably over the service period. From time to time, Duke Energy offers special termination benefits under voluntary severance programs. Special termination benefits are measured upon employee acceptance and recorded immediately absent a significant retention period. If a significant retention period exists, the cost of the special termination benefits are recorded ratably over the remaining service periods of the affected employees. Employee acceptance of voluntary severance benefits is determined by management based on the facts and circumstances of the special termination benefits being offered. See Note 21 for further information.
Guarantees	Guarantees. Upon issuance or modification of a guarantee, the Duke Energy Registrants recognize a liability at the time of issuance or material modification for the estimated fair value of the obligation it assumes under that guarantee, if any. Fair value is estimated using a probability-weighted approach. The Duke Energy Registrants reduce the obligation over the term of the guarantee or related contract in a systematic and rational method as risk is reduced under the obligation. Any additional contingent loss for guarantee contracts subsequent to the initial recognition of a liability in accordance with applicable accounting guidance is accounted for and recognized at the time a loss is probable and the amount of the loss can be reasonably estimated. The Duke Energy Registrants have entered into various indemnification agreements related to purchase and sale agreements and other types of contractual agreements with vendors and other third parties. These agreements typically cover environmental, tax, litigation and other matters, as well as breaches of representations, warranties and covenants. Typically, claims may be made by third parties for various periods of time, depending on the nature of the claim. Potential exposure under these indemnification agreements can range from a specified to an unlimited dollar amount, depending on the nature of the claim and the particular transaction. See Note 7 for further information.
Stock-based Compensation	Stock-Based Compensation. Stock-based compensation represents the cost related to stock-based awards granted to employees. Duke Energy recognizes stock-based compensation based upon the estimated fair value of the awards, net of estimated forfeitures. The recognition period for these costs begin at either the applicable service inception date or grant date and continues throughout the requisite service period, or for certain share-based awards until the employee becomes retirement eligible, if earlier. Share-based awards, including stock options, but not performance shares, granted to employees that are already retirement eligible are deemed to have vested immediately upon issuance, and, therefore, compensation cost for those awards is recognized on the date such awards are granted. See Note 22 for further information.
Accounting For Purchases And Sales Of Emission Allowances	Accounting For Purchases and Sales of Emission Allowances. Emission allowances are issued by the Environmental Protection Agency (EPA) at zero cost and permit the holder of the allowance to emit certain gaseous by-products of fossil fuel combustion, including sulfur dioxide (SO2) and nitrogen oxide (NOx). Allowances may also be bought and sold via third-party transactions. Allowances allocated to or acquired by the Duke Energy Registrants are held primarily for consumption. Emission allowances at cost are included in Intangibles, net on the Consolidated Balance Sheets and the Duke Energy Registrants recognize expense as the allowances are consumed or sold. Gains or losses on sales of emission allowances by regulated businesses that do not provide for direct recovery through a cost-tracking mechanism and by nonregulated businesses are presented in Gains on Sales of Other Assets and Other, net, in the Consolidated Statements of Operations. For regulated businesses that provide for direct recovery of emission allowances, any gain or loss on sales of recoverable emission allowances are included in the rate structure of the regulated entity and are deferred as a regulatory asset or liability. Future rates charged to retail customers are impacted by any gain or loss on sales of recoverable emission allowances. Purchases and sales of emission allowances are presented gross as investing activities on the Consolidated Statements of Cash Flows. See Note 12 for discussion regarding the impairment of the carrying value of certain emission allowances in 2011.
Income Taxes	Income Taxes. Duke Energy and its subsidiaries file a consolidated federal income tax return and other state and foreign jurisdictional returns as required. Deferred income taxes have been provided for temporary differences between the GAAP and tax carrying amounts of assets and liabilities. These differences create taxable or tax-deductible amounts for future periods. Investment tax credits (ITC) associated with regulated operations are deferred and are amortized as a reduction of income tax expense over the estimated useful lives of the related properties. The Subsidiary Registrants entered into a tax sharing agreement with Duke Energy, where the separate return method is used to allocate tax expenses and benefits to the subsidiaries whose investments or results of operations provide these tax expenses or benefits. The accounting for income taxes essentially represents the income taxes that the Subsidiary Registrants would incur if the Subsidiary Registrants were a separate company filing its own federal tax return as a C-Corporation. The Duke Energy Registrants record unrecognized tax benefits for positions taken or expected to be taken on tax returns, including the decision to exclude certain income or transactions from a return, when a more-likely-than-not threshold is met for a tax position and management believes that the position will be sustained upon examination by the taxing authorities. Management evaluates each position based solely on the technical merits and facts and circumstances of the position, assuming the position will be examined by a taxing authority having full knowledge of all relevant information. The Duke Energy Registrants record the largest amount of the unrecognized tax benefit that is greater than 50% likely of being realized upon settlement or effective settlement. Management considers a tax position effectively settled for the purpose of recognizing previously unrecognized tax benefits when the following conditions exist: (i) the taxing authority has completed its examination procedures, including all appeals and administrative reviews that the taxing authority is required and expected to perform for the tax positions, (ii) the Duke Energy Registrants do not intend to appeal or litigate any aspect of the tax position included in the completed examination, and (iii) it is remote that the taxing authority would examine or reexamine any aspect of the tax position. Deferred taxes are not provided on translation gains and losses where Duke Energy expects earnings of a foreign operation to be indefinitely reinvested. The Duke Energy Registrants record tax-related interest expense in Interest Expense and interest income and penalties in Other Income and Expenses, net, in the Consolidated Statements of Operations. See Note 24 for further information.
Excise Taxes	Excise Taxes. Certain excise taxes levied by state or local governments are collected by the Duke Energy Registrants from their customers. These taxes, which are required to be paid regardless of the Duke Energy Registrants' ability to collect from the customer, are accounted for on a gross basis. When the Duke Energy Registrants act as an agent, and the tax is not required to be remitted if it is not collected from the customer, the taxes are accounted for on a net basis. The Duke Energy Registrants' excise taxes accounted for on a gross basis and recorded as operating revenues in the Consolidated Statements of Operations were as follows:
Foreign Currency Transaction	Foreign Currency Translation. The local currencies of Duke Energy's foreign operations have been determined to be their functional currencies, except for certain foreign operations whose functional currency has been determined to be the U.S. Dollar, based on an assessment of the economic circumstances of the foreign operation. Assets and liabilities of foreign operations, except for those whose functional currency is the U.S. Dollar, are translated into U.S. Dollars at the exchange rates in effect at period end. Translation adjustments resulting from fluctuations in exchange rates are included as a separate component of AOCI. Revenue and expense accounts of these operations are translated at average exchange rates prevailing during the year. Gains and losses arising from balances and transactions denominated in currencies other than the functional currency are included in the results of operations in the period in which they occur.
Dividend Restrictions And Unappropriated Retained Earnings	Dividend Restrictions and Unappropriated Retained Earnings. Duke Energy does not have any legal, regulatory or other restrictions on paying common stock dividends to shareholders. However, as further described in Note 4, due to conditions established by regulators at the time of the Duke Energy/Cinergy merger in April 2006 and the Duke Energy/Progress Energy merger in 2012, certain wholly owned subsidiaries, including Duke Energy Carolinas, Progress Energy Carolinas, Duke Energy Ohio and Duke Energy Indiana, have restrictions on paying dividends or otherwise advancing funds to Duke Energy. At December 31, 2012 and 2011, an insignificant amount of Duke Energy's consolidated Retained earnings balance represents undistributed earnings of equity method investments.
New Accounting Standards [Policy Text Block]	New Accounting Standards. The following new accounting standards were adopted by the Duke Energy Registrants during the year ended December 31, 2012, and the impact of such adoption, if applicable, has been presented in the accompanying Consolidated Financial Statements: Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC) 220 — Comprehensive Income. In June 2011, the FASB amended the existing requirements for presenting comprehensive income in financial statements primarily to increase the prominence of items reported in other comprehensive income (OCI) and to facilitate the convergence of U.S. GAAP and International Financial Reporting Standards (IFRS). Specifically, the revised guidance eliminates the option previously provided to present components of OCI as part of the statement of changes in stockholders' equity. Accordingly, all non-owner changes in stockholders' equity are required to be presented either in a single continuous statement of comprehensive income or in two separate but consecutive financial statements. For the Duke Energy Registrants, this revised guidance was effective on a retrospective basis for interim and annual periods beginning January 1, 2012. The adoption of this standard changed the presentation of the Duke Energy Registrants' financial statements but did not affect the calculation of net income, comprehensive income or earnings per share. ASC 820 — Fair Value Measurements and Disclosures. In May 2011, the FASB amended existing requirements for measuring fair value and for disclosing information about fair value measurements. This revised guidance results in a consistent definition of fair value, as well as common requirements for measurement and disclosure of fair value information between U.S. GAAP and IFRS. In addition, the amendments set forth enhanced disclosure requirements with respect to recurring Level 3 measurements, nonfinancial assets measured or disclosed at fair value, transfers between levels in the fair value hierarchy, and assets and liabilities disclosed but not recorded at fair value. For the Duke Energy Registrants, the revised fair value measurement guidance was effective on a prospective basis for interim and annual periods beginning January 1, 2012. The adoption of this new guidance did not have a significant impact on the Duke Energy Registrants disclosures or their consolidated results of operations, cash flows, or financial position. The following new accounting standards were adopted by Duke Energy during the year ended December 31, 2011, and the impact of such adoption, if applicable has been presented in the accompanying Consolidated Financial Statements: ASC 605 — Revenue Recognition. In October 2009, the FASB issued new revenue recognition accounting guidance in response to practice concerns related to the accounting for revenue arrangements with multiple deliverables. This new accounting guidance primarily applies to all contractual arrangements in which a vendor will perform multiple revenue generating activities and addresses the unit of accounting for arrangements involving multiple deliverables, as well as how arrangement consideration should be allocated to the separate units of accounting. For the Duke Energy Registrants, the new accounting guidance was effective January 1, 2011, and applied on a prospective basis. This new accounting guidance did not have a material impact to the consolidated results of operations, cash flows or financial position of the Duke Energy Registrants. ASC 805 — Business Combinations. In November 2010, the FASB issued new accounting guidance in response to diversity in the interpretation of pro forma information disclosure requirements for business combinations. The new accounting guidance requires an entity to present pro forma financial information as if a business combination occurred at the beginning of the earliest period presented as well as additional disclosures describing the nature and amount of material, nonrecurring pro forma adjustments. This new accounting guidance was effective January 1, 2011, and has been applied to all business combinations consummated after that date. ASC 820 — Fair Value Measurements and Disclosures. In January 2010, the FASB amended existing fair value measurements and disclosures accounting guidance to clarify certain existing disclosure requirements and to require a number of additional disclosures, including amounts and reasons for significant transfers between the three levels of the fair value hierarchy, and presentation of certain information in the reconciliation of recurring Level 3 measurements on a gross basis. For the Duke Energy Registrants, certain portions of this revised accounting guidance were effective on January 1, 2010, with additional disclosures effective for periods beginning January 1, 2011. The adoption of this accounting guidance resulted in additional disclosure in the notes to the consolidated financial statements but did not have an impact on the Duke Energy Registrants' consolidated results of operations, cash flows or financial position. ASC 350 — Intangibles–Goodwill and Other. In September 2011, the FASB amended existing goodwill impairment testing accounting guidance to provide an entity testing goodwill for impairment with the option of performing a qualitative assessment prior to calculating the fair value of a reporting unit in step one of a goodwill impairment test. Under this revised guidance, a qualitative assessment would require an evaluation of economic, industry, and company-specific considerations. If an entity determines, on a basis of such qualitative factors, that the fair value of a reporting unit is more likely than not less than the carrying value of a reporting unit, the two-step impairment test, as required under pre-existing applicable accounting guidance, would be required. Otherwise, no further impairment testing would be required. The revised goodwill impairment testing accounting guidance is effective for the Duke Energy Registrants' annual and interim goodwill impairment tests performed for fiscal years beginning January 1, 2012, with early adoption of this revised guidance permitted for annual and interim goodwill impairment tests performed as of a date before September 15, 2011. Since annual goodwill impairment tests are performed by Duke Energy as of August 31, the Duke Energy Registrants early adopted this revised accounting guidance during the third quarter of 2011 and applied that guidance to their annual goodwill impairment tests for 2011. The following new accounting standards were adopted by Duke Energy during the year ended December 31, 2010, and the impact of such adoption, if applicable has been presented in the accompanying Consolidated Financial Statements: ASC 860 — Transfers and Servicing. In June 2009, the FASB issued revised accounting guidance for transfers and servicing of financial assets and extinguishment of liabilities, to require additional information about transfers of financial assets, including securitization transactions, as well as additional information about an enterprise's continuing exposure to the risks related to transferred financial assets. This revised accounting guidance eliminated the concept of a Qualifying Special Purpose Entity (QSPE) and required those entities which were not subject to consolidation under previous accounting rules to now be assessed for consolidation. In addition, this accounting guidance clarified and amended the derecognition criteria for transfers of financial assets (including transfers of portions of financial assets) and required additional disclosures about a transferor's continuing involvement in transferred financial assets. For Duke Energy, this revised accounting guidance was effective prospectively for transfers of financial assets occurring on or after January 1, 2010, and early adoption of this statement was prohibited. Since 2002, Duke Energy Ohio, Duke Energy Indiana, and Duke Energy Kentucky have sold, on a revolving basis, nearly all of their accounts receivable and related collections through CRC, a bankruptcy-remote QSPE. The securitization transaction was structured to meet the criteria for sale accounting treatment, and, accordingly, Duke Energy did not consolidate CRC, and the transfers were accounted for as sales. Effective with adoption of this revised accounting guidance and ASC 810-Consolidation, as discussed below, the accounting treatment and/or financial statement presentation of Duke Energy's accounts receivable securitization programs was impacted as Duke Energy began consolidating CRC effective January 1, 2010. Duke Energy Ohio's and Duke Energy Indiana's sales of accounts receivable and related financial statement presentation were not impacted by the adoption of ASC 860. ASC 810 — Consolidations. In June 2009, the FASB amended existing consolidation accounting guidance to eliminate the exemption from consolidation for QSPEs, and clarified, but did not significantly change, the criteria for determining whether an entity meets the definition of a VIE. This revised accounting guidance also required an enterprise to qualitatively assess the determination of the primary beneficiary of a VIE based on whether that enterprise has both the power to direct the activities that most significantly impact the economic performance of a VIE and the obligation to absorb losses or the right to receive benefits of a VIE that could potentially be significant to a VIE. In addition, this revised accounting guidance modified existing accounting guidance to require an ongoing evaluation of a VIE's primary beneficiary and amended the types of events that trigger a reassessment of whether an entity is a VIE. Furthermore, this accounting guidance required enterprises to provide additional disclosures about their involvement with VIEs and any significant changes in their risk exposure due to that involvement. For the Duke Energy Registrants, this accounting guidance was effective beginning on January 1, 2010, and is applicable to all entities in which Duke Energy is involved, including entities previously subject to existing accounting guidance for VIEs, as well as any QSPEs that existed as of the effective date. Effective with adoption of this revised accounting guidance, the accounting treatment and/or financial statement presentation of Duke Energy's accounts receivable securitization programs were impacted as Duke Energy began consolidating CRC effective January 1, 2010. Duke Energy Ohio's and Duke Energy Indiana's sales of accounts receivable and related financial statement presentation were not impacted by the adoption of ASC 810. This revised accounting guidance did not have a significant impact on any of the Duke Energy Registrants' other interests in VIEs. ASC 820 — Fair Value Measurements and Disclosures. In January 2010, the FASB amended existing fair value measurements and disclosures accounting guidance to clarify certain existing disclosure requirements and to require a number of additional disclosures, including amounts and reasons for significant transfers between the three levels of the fair value hierarchy, and presentation of certain information in the reconciliation of recurring Level 3 measurements on a gross basis. For the Duke Energy Registrants, certain portions of this revised accounting guidance were effective on January 1, 2010, with additional disclosures effective for periods beginning January 1, 2011. The initial adoption of this accounting guidance resulted in additional disclosure in the notes to the consolidated financial statements but did not have an impact on the Duke Energy Registrants' consolidated results of operations, cash flows or financial position. The following new Accounting Standards Updates (ASU) have been issued, but have not yet been adopted by Duke Energy, as of December 31, 2012. ASC 210 — Balance Sheet. In December 2011, the FASB issued revised accounting guidance to amend the existing disclosure requirements for offsetting financial assets and liabilities to enhance current disclosures, as well as to improve comparability of balance sheets prepared under U.S. GAAP and IFRS. The revised disclosure guidance affects all companies that have financial instruments and derivative instruments that are either offset in the balance sheet (i.e., presented on a net basis) or subject to an enforceable master netting arrangement and/or similar agreement. The revised guidance requires that certain enhanced quantitative and qualitative disclosures be made with respect to a company's netting arrangements and/or rights of setoff associated with its financial instruments and/or derivative instruments including associated collateral. For the Duke Energy Registrants, the revised disclosure guidance is effective on a retrospective basis for interim and annual periods beginning January 1, 2013. Other than additional disclosures, this revised guidance does not impact the Duke Energy Registrants' consolidated results of operations, cash flows or financial position. ASC 220 — Comprehensive Income. In February 2013, the FASB amended the existing requirements for presenting comprehensive income in financial statements to improve the reporting of reclassifications out of AOCI. The amendments in this Update seek to attain that objective by requiring an entity to report the effect of significant reclassifications out of AOCI on the respective line items in net income if the amount being reclassified is required under U.S. GAAP to be reclassified in its entirety to net income. For other amounts that are not required under U.S. GAAP to be reclassified in their entirety to net income in the same reporting period, an entity is required to cross-reference other disclosures required under U.S. GAAP that provide additional detail about those amounts. This would be the case when a portion of the amount reclassified out of AOCI is reclassified to a balance sheet account (for example, inventory) instead of directly to income or expense in the same reporting period. For the Duke Energy Registrants, this revised guidance is effective on a prospective basis for interim and annual periods beginning January 1, 2013. Other than additional disclosures or a change in the presentation on the statement of comprehensive income, this revised guidance does not impact the Duke Energy Registrants' consolidated results of operations, cash flows or financial position.
Progress Energy Florida [Member]
Policy Text Block [Line Items]
Organization	Nature of Operations and Basis of Consolidation. Duke Energy Corporation (collectively with its subsidiaries, Duke Energy), is an energy company headquartered in Charlotte, North Carolina. Duke Energy operates in the United States (U.S.) and Latin America primarily through its direct and indirect subsidiaries. Duke Energy's subsidiaries included Duke Energy Carolinas, LLC (Duke Energy Carolinas), Duke Energy Ohio, Inc. (Duke Energy Ohio), which includes Duke Energy Kentucky, Inc. (Duke Energy Kentucky), and Duke Energy Indiana, Inc. (Duke Energy Indiana) prior to the merger with Progress Energy, Inc. (Progress Energy). On July 2, 2012, Duke Energy merged with Progress Energy, with Duke Energy continuing as the surviving corporation, and Progress Energy becoming a subsidiary of Duke Energy. Carolina Power & Light Company d/b/a Progress Energy Carolinas, Inc. (Progress Energy Carolinas) and Florida Power Corporation d/b/a Progress Energy Florida, Inc. (Progress Energy Florida), Progress Energy's regulated utility subsidiaries, are now indirect subsidiaries of Duke Energy. Duke Energy's consolidated financial statements include Progress Energy, Progress Energy Carolinas and Progress Energy Florida activity beginning July 2, 2012. See Note 2 for additional information regarding the merger. When discussing Duke Energy's consolidated financial information, it necessarily includes the results of its six separate subsidiary registrants, Duke Energy Carolinas, Progress Energy, Progress Energy Carolinas, Progress Energy Florida, Duke Energy Ohio and Duke Energy Indiana (collectively referred to as the Subsidiary Registrants), which, along with Duke Energy, are collectively referred to as the Duke Energy Registrants. Progress Energy, Progress Energy Carolinas and Progress Energy Florida (collectively referred to as the Progress Energy Registrants) continue to maintain reporting requirements as SEC registrants. In accordance with SEC guidance, the Progress Energy Registrants did not reflect the impacts of acquisition accounting from the merger with Duke Energy, whereby the adjustments of assets and liabilities to fair value and the resultant goodwill would be shown on the financial statements of the Progress Energy Registrants. These adjustments were recorded by Duke Energy. The information in these combined notes relates to each of the Duke Energy Registrants as noted in the Index to the Combined Notes. However, none of the registrants makes any representation as to information related solely to Duke Energy or the subsidiaries of Duke Energy other than itself. As discussed further in Note 3, Duke Energy operates three reportable business segments: U.S. Franchised Electric and Gas (USFE&G), Commercial Power and International Energy. The remainder of Duke Energy's operations is presented as Other. These Consolidated Financial Statements include, after eliminating intercompany transactions and balances, the accounts of the Duke Energy Registrants and all majority-owned subsidiaries where the respective Duke Energy Registrants have control and those variable interest entities (VIEs) where the respective Duke Energy Registrants are the primary beneficiary. These Consolidated Financial Statements also reflect the Duke Energy Registrants' proportionate share of certain generation and transmission facilities. In January 2012, Duke Energy Ohio completed the sale of its 75% ownership of the Vermillion Generating Station (Vermillion); upon the close, Duke Energy Indiana purchased a 62.5% interest in the station. See Note 2 for further discussion. Duke Energy Carolinas, a wholly owned subsidiary of Duke Energy, is an electric utility company that generates, transmits, distributes and sells electricity in North Carolina and South Carolina. Duke Energy Carolinas is subject to the regulatory provisions of the North Carolina Utilities Commission (NCUC), the Public Service Commission of South Carolina (PSCSC), the U.S. Nuclear Regulatory Commission (NRC) and the Federal Energy Regulatory Commission (FERC). Substantially all of Duke Energy Carolinas' operations are regulated and qualify for regulatory accounting treatment. As discussed further in Note 3, Duke Energy Carolinas' operations include one reportable business segment, Franchised Electric. Progress Energy, a wholly owned subsidiary of Duke Energy, is a holding company headquartered in Raleigh, North Carolina, subject to regulation by the FERC. Progress Energy conducts operations through its wholly owned subsidiaries, Progress Energy Carolinas and Progress Energy Florida. As discussed further in Note 3, Progress Energy's operations include one reportable segment, Franchised Electric. Progress Energy Carolinas, an indirect wholly owned subsidiary of Duke Energy, is a regulated public utility primarily engaged in the generation, transmission, distribution and sale of electricity in portions of North Carolina and South Carolina. Progress Energy Carolinas is subject to the regulatory provisions of the NCUC, the PSCSC, the NRC and the FERC. Substantially all of Progress Energy Carolinas' operations are regulated and qualify for regulatory accounting treatment. As discussed further in Note 3, Progress Energy Carolinas' operations include one reportable segment, Franchised Electric. Progress Energy Florida, an indirect wholly owned subsidiary of Duke Energy, is a regulated public utility primarily engaged in the generation, transmission, distribution and sale of electricity in west central Florida. Progress Energy Florida is subject to the regulatory jurisdiction of the Florida Public Service Commission (FPSC), the NRC and the FERC. Substantially all of Progress Energy Florida's operations are regulated and qualify for regulatory accounting treatment. As discussed further in Note 3, Progress Energy Florida's operations include one reportable segment, Franchised Electric. Duke Energy Ohio, an indirect wholly owned subsidiary of Duke Energy, is a combination electric and gas public utility that provides service in the southwestern portion of Ohio and in northern Kentucky through its wholly owned subsidiary, Duke Energy Kentucky, as well as electric generation in parts of Ohio, Illinois and Pennsylvania. Duke Energy Ohio's principal lines of business include generation, transmission and distribution of electricity, the sale of and/or transportation of natural gas, and energy marketing. Duke Energy Ohio conducts competitive auctions for retail electricity supply in Ohio whereby the energy price is recovered from retail customers. Duke Energy Kentucky's principal lines of business include generation, transmission and distribution of electricity, as well as the sale of and/or transportation of natural gas. References herein to Duke Energy Ohio include Duke Energy Ohio and its subsidiaries, unless otherwise noted. Duke Energy Ohio is subject to the regulatory provisions of the Public Utilities Commission of Ohio (PUCO), the Kentucky Public Service Commission (KPSC) and the FERC. Duke Energy Ohio applies regulatory accounting treatment to substantially all of the operations in its Franchised Electric and Gas operating segment. Through November 2011, Duke Energy Ohio applied regulatory accounting treatment to certain rate riders associated with retail generation of its Commercial Power operating segment. See Note 3 for further information about Duke Energy Ohio's business segments. Duke Energy Indiana, an indirect wholly owned subsidiary of Duke Energy, is an electric utility that provides service in north central, central, and southern Indiana. Its primary line of business is generation, transmission and distribution of electricity. Duke Energy Indiana is subject to the regulatory provisions of the Indiana Utility Regulatory Commission (IURC) and the FERC. Substantially all of Duke Energy Indiana's operations are regulated and qualify for regulatory accounting treatment. As discussed further in Note 3, Duke Energy Indiana's operations include one reportable business segment, Franchised Electric. Certain prior year amounts have been reclassified to conform to current year presentation. In addition, prior year financial statements and footnote disclosures for the Progress Energy Registrants have been reclassified to conform to Duke Energy's presentation.
Use Of Estimates	Use of Estimates. To conform to generally accepted accounting principles (GAAP) in the U.S., management makes estimates and assumptions that affect the amounts reported in the Consolidated Financial Statements and Notes. Although these estimates are based on management's best available information at the time, actual results could differ.
Cost-Based Regulation	Cost-Based Regulation. The Duke Energy Registrants account for their regulated operations in accordance with applicable regulatory accounting guidance. The economic effects of regulation can result in a regulated company recording assets for costs that have been or are expected to be approved for recovery from customers in a future period or recording liabilities for amounts that are expected to be returned to customers in the rate-setting process in a period different from the period in which the amounts would be recorded by an unregulated enterprise. Accordingly, the Duke Energy Registrants record assets and liabilities that result from the regulated ratemaking process that would not be recorded under GAAP for nonregulated entities. Regulatory assets and liabilities are amortized consistent with the treatment of the related cost in the ratemaking process. Management continually assesses whether regulatory assets are probable of future recovery by considering factors such as applicable regulatory changes, recent rate orders applicable to other regulated entities and the status of any pending or potential deregulation legislation. Additionally, management continually assesses whether any regulatory liabilities have been incurred. Based on this continual assessment, management believes the existing regulatory assets are probable of recovery and that no regulatory liabilities, other than those recorded, have been incurred. These regulatory assets and liabilities are classified in the Consolidated Balance Sheets as Regulatory assets and Other in Current Assets and as Regulatory liabilities and Other in Current Liabilities, respectively. The Duke Energy Registrants periodically evaluate the applicability of regulatory accounting treatment by considering factors such as regulatory changes and the impact of competition. If cost-based regulation ends or competition increases, the Duke Energy Registrants may have to reduce their asset balances to reflect a market basis less than cost and write-off the associated regulatory assets and liabilities. If it becomes probable that part of the cost of a plant under construction or a recently completed plant will be disallowed for ratemaking purposes and a reasonable estimate of the amount of the disallowance can be made, that amount is recognized as a loss. In November 2011, in conjunction with the PUCO's approval of its new Electric Security Plan (ESP), Duke Energy Ohio ceased applying regulatory accounting treatment to generation operations within its Commercial Power segment. For further information, see Note 4.
Energy Purchases, Fuel Costs And Fuel Cost Deferrals	Energy Purchases, Fuel Costs and Fuel Cost Deferrals. The Duke Energy Registrants utilize cost-tracking mechanisms, commonly referred to as a fuel adjustment clause, to recover the retail portion of fuel and purchased power. The Duke Energy Registrants defer the related cost through Fuel used in electric generation and purchased power — regulated on the Consolidated Statement of Operations, unless a regulatory requirement exists for deferral through Operating Revenues. Fuel used in electric generation and purchased power — regulated includes fuel, purchased power and recoverable costs that are deferred through fuel clauses established by the Subsidiary Registrants' regulators. These clauses allow the Subsidiary Registrants to recover fuel costs, fuel-related costs and portions of purchased power costs through surcharges on customer rates. The Subsidiary Registrants record any under-recovery or over-recovery resulting from the differences between estimated and actual costs as a regulatory asset or regulatory liability until billed or refunded to customers, at which point the differences are adjusted through revenues. Indiana law limits the amount of fuel costs that Duke Energy Indiana can recover to an amount that will not result in earning a return in excess of that allowed by the IURC. As discussed in Note 4, beginning January 1, 2012, Duke Energy Ohio procures energy for its retail customers through a third-party auction. Purchases of energy through the auction process are a pass-through of costs for Duke Energy Ohio, with no affect on earnings. Subsequent to December 31, 2011, Duke Energy Ohio's generation assets are no longer dedicated to retail customers and, accordingly, Duke Energy Ohio can no longer recover their generation assets' energy purchases and fuel costs from regulated customers.
Cash and Cash Equivalents	Cash and Cash Equivalents. All highly liquid investments with maturities of three months or less at the date of acquisition are considered cash equivalents. At December 31, 2012, Duke Energy had cash and cash equivalents of $1,424 million, of which $731 million is held in foreign jurisdictions and is forecasted to be used to fund international operations and investments
Restricted Cash	Restricted Cash. The Duke Energy Registrants have restricted cash related primarily to collateral assets, escrow deposits, and restricted cash of VIEs. Restricted cash balances are reflected in Other within Current Assets and in Other within Investments and Other Assets on the Consolidated Balance Sheets.
Inventory	Inventory. Inventory is comprised of amounts presented in the tables below and is recorded primarily using the average cost method. Inventory related to the Duke Energy Registrants' regulated operations is valued at historical cost consistent with ratemaking treatment. Materials and supplies are recorded as inventory when purchased and subsequently charged to expense or capitalized to property, plant and equipment when installed. Reserves are established for excess and obsolete inventory. Inventory related to the Duke Energy Registrants' nonregulated operations is valued at the lower of cost or market. The following tables present the Duke Energy Registrants' inventory.
Investments In Debt And Equity Securities	Investments in Debt and Equity Securities. The Duke Energy Registrants classify investments into two categories — trading and available-for-sale. Trading securities are reported at fair value in the Consolidated Balance Sheets with net realized and unrealized gains and losses included in earnings each period. Available-for-sale securities are also reported at fair value on the Consolidated Balance Sheets with unrealized gains and losses included in Accumulated Other Comprehensive Income (AOCI) or as a regulatory asset or liability, unless it is determined that the carrying value of an investment is other-than-temporarily impaired. Other-than-temporary impairments related to equity securities and the credit loss portion of debt securities are included in earnings, unless deferred in accordance with regulatory accounting treatment. Investments in debt and equity securities are classified as either short-term investments or long-term investments based on management's intent and ability to sell these securities, taking into consideration illiquidity factors in the current markets with respect to certain investments that have historically provided for a high degree of liquidity, such as investments in auction rate debt securities. See Note 17 for further information on the investments in debt and equity securities, including investments held in the nuclear decommissioning trust funds (NDTF).
Long-Lived Asset Impairments	Long-Lived Asset Impairments. The Duke Energy Registrants evaluate whether long-lived assets, excluding goodwill, have been impaired when circumstances indicate the carrying value of those assets may not be recoverable. For such long-lived assets, an impairment exists when its carrying value exceeds the sum of estimates of the undiscounted cash flows expected to result from the use and eventual disposition of the asset. When alternative courses of action to recover the carrying amount of a long-lived asset are under consideration, a probability-weighted approach is used for developing estimates of future undiscounted cash flows. If the carrying value of the long-lived asset is not recoverable based on these estimated future undiscounted cash flows, the impairment loss is measured as the excess of the carrying value of the asset over its fair value, such that the asset's carrying value is adjusted to its estimated fair value. Management assesses the fair value of long-lived assets using commonly accepted techniques, and may use more than one source. Sources to determine fair value include, but are not limited to, recent third party comparable sales, internally developed discounted cash flow analysis and analysis from outside advisors. Significant changes in market conditions resulting from events such as, among others, changes in commodity prices or the condition of an asset, or a change in management's intent to utilize the asset are generally viewed by management as triggering events to re-assess the cash flows related to the long-lived assets. See Note 12 for further information.
Property, Plant and Equipment	Property, Plant and Equipment. Property, plant and equipment are stated at the lower of historical cost less accumulated depreciation or fair value, if impaired. The Duke Energy Registrants capitalize all construction-related direct labor and material costs, as well as indirect construction costs. Indirect costs include general engineering, taxes and the allowance for funds used during construction (AFUDC). See “AFUDC and Interest Capitalized,” below for additional information. The cost of renewals and betterments that extend the useful life of property, plant and equipment are also capitalized. The cost of repairs, replacements and major maintenance projects, which do not extend the useful life or increase the expected output of the asset, are expensed as incurred. Depreciation is generally computed over the estimated useful life of the asset using the composite straight-line method. For regulated operations, depreciation studies are conducted periodically to update the composite rates and are approved by the various state commissions. The composite weighted-average depreciation rates, excluding nuclear fuel, for each of the Duke Energy Registrants are included in the following table: When the Duke Energy Registrants retire regulated property, plant and equipment under what is considered a normal retirement, the original cost plus the cost of retirement, less salvage value, is charged to accumulated depreciation, consistent with regulated rate-making practices. When it becomes probable that a regulated generation asset will be retired substantially in advance of its original expected useful life or is abandoned, the cost of the asset and the corresponding accumulated depreciation is removed from Cost and Accumulated depreciation and amortization within Property, Plant and Equipment on the Consolidated Balance Sheets and a separate asset is recognized. If the plant is still in operation, the amount is classified as Generation facilities to be retired, net on the Consolidated Balance Sheets. If the plant is no longer operating, then a regulatory asset is recognized. The carrying value of the asset is based on historical cost if the Duke Energy Registrants are allowed to recover the remaining net book value and a full return on the asset. If the Duke Energy Registrants do not expect to recover the full remaining cost and a full return, the carrying value of the asset is based on the lower of cost or the present value of the future revenues expected to be provided to recover the allowable costs discounted at the Duke Energy Registrants' incremental borrowing rate. An impairment is recognized if the net book value of the asset exceeds the present value of the future revenues to be recovered in rates. When the Duke Energy Registrants sell entire regulated operating units, or retire or sell nonregulated properties, the original cost is removed from property and the related accumulated depreciation and amortization balances are reduced. Any gain or loss is recorded in earnings, unless otherwise required by the applicable regulatory body. See Note 10 for further information on the components and estimated useful lives of Duke Energy's property, plant and equipment.
Nuclear Fuel	Nuclear Fuel. Nuclear fuel is classified as Property, Plant and Equipment in the Consolidated Balance Sheets. Nuclear fuel in the front-end fuel processing phase is considered work in progress and not amortized until placed in service. Amortization of nuclear fuel is included within Fuel used in electric generation and purchased power-regulated in the Consolidated Statements of Operations. The amortization is recorded using the units-of-production method.
AFUDC And Interest Capitalized	AFUDC and Interest Capitalized. In accordance with applicable regulatory accounting guidance, the Duke Energy Registrants record AFUDC, which represents the estimated debt and equity costs of capital funds necessary to finance the construction of new regulated facilities. The equity component of AFUDC is a non-cash amount within the Consolidated Statements of Operations. AFUDC is capitalized as a component of the cost of property, plant and equipment, with an offsetting credit to Other income and expenses, net on the Consolidated Statements of Operations for the equity component and as an offset to Interest Expense on the Consolidated Statements of Operations for the debt component. After construction is completed, the Duke Energy Registrants are permitted to recover these costs through inclusion in the rate base and the corresponding depreciation expense or nuclear fuel expense. AFUDC equity is a permanent difference item for income tax purposes, thus reducing the Duke Energy Registrants' effective tax rate during the construction phase in which AFUDC equity is being recorded. The effective tax rate is subsequently increased in future periods when the completed property, plant and equipment are placed in service and depreciation of the AFUDC equity commences. See Note 24 for information related to the impacts of AFUDC equity on the Duke Energy Registrants' effective tax rate. For nonregulated operations, interest is capitalized during the construction phase in accordance with the applicable accounting guidance.
Asset Retirement Obligations	Asset Retirement Obligations. The Duke Energy Registrants recognize asset retirement obligations for legal obligations associated with the retirement of long-lived assets that result from the acquisition, construction, development and/or normal use of the asset, and for conditional asset retirement obligations. The term conditional asset retirement obligation refers to a legal obligation to perform an asset retirement activity in which the timing and (or) method of settlement are conditional on a future event that may or may not be within the control of the entity. The obligation to perform the asset retirement activity is unconditional even though uncertainty exists about the timing and (or) method of settlement. Thus, the timing and (or) method of settlement may be conditional on a future event. When recording an asset retirement obligation, the present value of the projected liability is recognized in the period in which it is incurred, if a reasonable estimate of fair value can be made. The liability is then accreted over time by applying an interest method of allocation to the liability. Substantially all accretion is related to regulated operations and is deferred pursuant to regulatory accounting. The present value of the liability is added to the carrying amount of the associated asset and this additional carrying amount is depreciated over the remaining life of the asset. The present value of the initial obligation and subsequent updates are based on discounted cash flows, which include estimates regarding the timing of future cash flows, the selection of discount rates and cost escalation rates, among other factors. These underlying assumptions and estimates are made as of a point in time and are subject to change. The obligations for nuclear decommissioning are based on site-specific cost studies. Duke Energy Carolinas and Progress Energy Carolinas assume prompt dismantlement of the nuclear facilities, which reflects dismantling the site after operations are ceased. Progress Energy Florida assumes the nuclear facility will be placed into a safe storage configuration until the eventual dismantling of the site begins in approximately 40-60 years. The nuclear decommissioning asset retirement obligation also assumes Duke Energy Carolinas, Progress Energy Carolinas and Progress Energy Florida will store spent fuel on site until such time that it can be transferred to a U.S. Department of Energy (DOE) facility. See Note 9 for further information.
Unbilled Revenue	Revenue Recognition and Unbilled Revenue. Revenues on sales of electricity and gas are recognized when either the service is provided or the product is delivered. Unbilled retail revenues are estimated by applying average revenue per kilowatt-hour (kWh) or per thousand cubic feet (Mcf) for all customer classes to the number of estimated kWh or Mcf delivered but not billed. Unbilled wholesale energy revenues are calculated by applying the contractual rate per megawatt-hour (MWh) to the number of estimated MWh delivered but not yet billed. Unbilled wholesale demand revenues are calculated by applying the contractual rate per megawatt (MW) to the MW volume delivered but not yet billed. The amount of unbilled revenues can vary significantly from period to period as a result of numerous factors, including seasonality, weather, customer usage patterns and customer mix. The Duke Energy Registrants had unbilled revenues within Receivables and within Restricted receivables of variable interest entities on their respective Consolidated Balance Sheets as shown in the table below.
Accounting For Risk Management, Hedging Activities And Financial Instruments	Accounting for Risk Management, Hedging Activities and Financial Instruments. The Duke Energy Registrants may use a number of different derivative and non-derivative instruments in connection with their commodity price, interest rate and foreign currency risk management activities, including swaps, futures, forwards and options. All derivative instruments except those that qualify for the normal purchase/normal sale (NPNS) exception within the accounting guidance for derivatives are recorded on the Consolidated Balance Sheets at their fair value. The effective portion of the change in the fair value of derivative instruments designated as cash flow hedges is recorded in AOCI. The effective portion of the change in the fair value of a fair value hedge is offset in net income by changes in the hedged item. The Duke Energy Registrants may designate qualifying derivative instruments as either cash flow hedges or fair value hedges, while others either have not been designated as hedges or do not qualify as a hedge (hereinafter referred to as undesignated contracts). For all contracts accounted for as a hedge, the Duke Energy Registrants prepare formal documentation of the hedge in accordance with the accounting guidance for derivatives. In addition, at inception and at least every three months thereafter, the Duke Energy Registrants formally assess whether the hedge contract is highly effective in offsetting changes in cash flows or fair values of hedged items. The Duke Energy Registrants document hedging activity by transaction type and risk management strategy. See Note 15 for further information.
Captive Insurance Reserves	Captive Insurance Reserves. Duke Energy has captive insurance subsidiaries that provide coverage, on an indemnity basis, to the Subsidiary Registrants as well as certain third parties, on a limited basis, for various business risks and losses, such as property, business interruption, workers' compensation and general liability. Liabilities include provisions for estimated losses incurred but not yet reported (IBNR), as well as provisions for known claims which have been estimated on a claims-incurred basis. IBNR reserve estimates involve the use of assumptions and are primarily based upon historical loss experience, industry data and other actuarial assumptions. Reserve estimates are adjusted in future periods as actual losses differ from historical experience. Duke Energy, through its captive insurance entities, also has reinsurance coverage with third parties, which provides reimbursement for certain losses above a per occurrence and/or aggregate retention. Duke Energy recognizes a reinsurance receivable for recovery of incurred losses under its captive's reinsurance coverage once realization of the receivable is deemed probable.
Unamortized Debt Premium, Discount And Expense	Unamortized Debt Premium, Discount and Expense. Premiums, discounts and expenses incurred with the issuance of outstanding long-term debt are amortized over the terms of the debt issues. Any call premiums or unamortized expenses associated with refinancing higher-cost debt obligations used to finance regulated assets and operations are amortized consistent with regulatory treatment of those items, where appropriate. The amortization expense is recorded as a component of Interest Expense in the Consolidated Statements of Operations and is reflected as Depreciation, amortization and accretion within Net cash provided by operating activities on the Consolidated Statements of Cash Flows.
Loss Contingencies And Environmental Liabilities	Loss Contingencies and Environmental Liabilities. The Duke Energy Registrants are involved in certain legal and environmental matters that arise in the normal course of business. Contingent losses are recorded when it is determined that it is probable that a loss has occurred and the amount of the loss can be reasonably estimated. When a range of the probable loss exists and no amount within the range is a better estimate than any other amount, the Duke Energy Registrants record a loss contingency at the minimum amount in the range. Unless otherwise required by GAAP, legal fees are expensed as incurred. Environmental liabilities are recorded on an undiscounted basis when the necessity for environmental remediation becomes probable and the costs can be reasonably estimated, or when other potential environmental liabilities are reasonably estimable and probable. The Duke Energy Registrants expense environmental expenditures related to conditions caused by past operations that do not generate current or future revenues. Certain environmental expenses receive regulatory accounting treatment, under which the expenses are recorded as regulatory assets. Environmental expenditures related to operations that generate current or future revenues are expensed or capitalized, as appropriate. See Note 5 for further information.
Pension And Other Post-Retirement Benefit Plans	Pension and Other Post-Retirement Benefit Plans. Duke Energy maintains qualified, non-qualified and other post-retirement benefit plans. Eligible employees of the Subsidiary Registrants participate in the respective Duke Energy or Progress Energy qualified, non-qualified and other post-retirement benefit plans and are allocated their proportionate share of benefit costs. See Note 23 for information related to Duke Energy's benefit plans, including certain accounting policies associated with these plans.
Severance And Special Termination Benefits	Severance and Special Termination Benefits. Duke Energy has an ongoing severance plan under which, in general, the longer a terminated employee worked prior to termination the greater the amount of severance benefits. The Duke Energy Registrants record a liability for involuntary severance once an involuntary severance plan is committed to by management, or sooner, if involuntary severances are probable and the related severance benefits can be reasonably estimated. For involuntary severance benefits that are incremental to its ongoing severance plan benefits, Duke Energy measures the obligation and records the expense at its fair value at the communication date if there are no future service requirements, or, if future service is required to receive the termination benefit, ratably over the service period. From time to time, Duke Energy offers special termination benefits under voluntary severance programs. Special termination benefits are measured upon employee acceptance and recorded immediately absent a significant retention period. If a significant retention period exists, the cost of the special termination benefits are recorded ratably over the remaining service periods of the affected employees. Employee acceptance of voluntary severance benefits is determined by management based on the facts and circumstances of the special termination benefits being offered. See Note 21 for further information.
Guarantees	Guarantees. Upon issuance or modification of a guarantee, the Duke Energy Registrants recognize a liability at the time of issuance or material modification for the estimated fair value of the obligation it assumes under that guarantee, if any. Fair value is estimated using a probability-weighted approach. The Duke Energy Registrants reduce the obligation over the term of the guarantee or related contract in a systematic and rational method as risk is reduced under the obligation. Any additional contingent loss for guarantee contracts subsequent to the initial recognition of a liability in accordance with applicable accounting guidance is accounted for and recognized at the time a loss is probable and the amount of the loss can be reasonably estimated. The Duke Energy Registrants have entered into various indemnification agreements related to purchase and sale agreements and other types of contractual agreements with vendors and other third parties. These agreements typically cover environmental, tax, litigation and other matters, as well as breaches of representations, warranties and covenants. Typically, claims may be made by third parties for various periods of time, depending on the nature of the claim. Potential exposure under these indemnification agreements can range from a specified to an unlimited dollar amount, depending on the nature of the claim and the particular transaction. See Note 7 for further information.
Stock-based Compensation	Stock-Based Compensation. Stock-based compensation represents the cost related to stock-based awards granted to employees. Duke Energy recognizes stock-based compensation based upon the estimated fair value of the awards, net of estimated forfeitures. The recognition period for these costs begin at either the applicable service inception date or grant date and continues throughout the requisite service period, or for certain share-based awards until the employee becomes retirement eligible, if earlier. Share-based awards, including stock options, but not performance shares, granted to employees that are already retirement eligible are deemed to have vested immediately upon issuance, and, therefore, compensation cost for those awards is recognized on the date such awards are granted. See Note 22 for further information.
Accounting For Purchases And Sales Of Emission Allowances	Accounting For Purchases and Sales of Emission Allowances. Emission allowances are issued by the Environmental Protection Agency (EPA) at zero cost and permit the holder of the allowance to emit certain gaseous by-products of fossil fuel combustion, including sulfur dioxide (SO2) and nitrogen oxide (NOx). Allowances may also be bought and sold via third-party transactions. Allowances allocated to or acquired by the Duke Energy Registrants are held primarily for consumption. Emission allowances at cost are included in Intangibles, net on the Consolidated Balance Sheets and the Duke Energy Registrants recognize expense as the allowances are consumed or sold. Gains or losses on sales of emission allowances by regulated businesses that do not provide for direct recovery through a cost-tracking mechanism and by nonregulated businesses are presented in Gains on Sales of Other Assets and Other, net, in the Consolidated Statements of Operations. For regulated businesses that provide for direct recovery of emission allowances, any gain or loss on sales of recoverable emission allowances are included in the rate structure of the regulated entity and are deferred as a regulatory asset or liability. Future rates charged to retail customers are impacted by any gain or loss on sales of recoverable emission allowances. Purchases and sales of emission allowances are presented gross as investing activities on the Consolidated Statements of Cash Flows. See Note 12 for discussion regarding the impairment of the carrying value of certain emission allowances in 2011.
Income Taxes	Income Taxes. Duke Energy and its subsidiaries file a consolidated federal income tax return and other state and foreign jurisdictional returns as required. Deferred income taxes have been provided for temporary differences between the GAAP and tax carrying amounts of assets and liabilities. These differences create taxable or tax-deductible amounts for future periods. Investment tax credits (ITC) associated with regulated operations are deferred and are amortized as a reduction of income tax expense over the estimated useful lives of the related properties. The Subsidiary Registrants entered into a tax sharing agreement with Duke Energy, where the separate return method is used to allocate tax expenses and benefits to the subsidiaries whose investments or results of operations provide these tax expenses or benefits. The accounting for income taxes essentially represents the income taxes that the Subsidiary Registrants would incur if the Subsidiary Registrants were a separate company filing its own federal tax return as a C-Corporation. The Duke Energy Registrants record unrecognized tax benefits for positions taken or expected to be taken on tax returns, including the decision to exclude certain income or transactions from a return, when a more-likely-than-not threshold is met for a tax position and management believes that the position will be sustained upon examination by the taxing authorities. Management evaluates each position based solely on the technical merits and facts and circumstances of the position, assuming the position will be examined by a taxing authority having full knowledge of all relevant information. The Duke Energy Registrants record the largest amount of the unrecognized tax benefit that is greater than 50% likely of being realized upon settlement or effective settlement. Management considers a tax position effectively settled for the purpose of recognizing previously unrecognized tax benefits when the following conditions exist: (i) the taxing authority has completed its examination procedures, including all appeals and administrative reviews that the taxing authority is required and expected to perform for the tax positions, (ii) the Duke Energy Registrants do not intend to appeal or litigate any aspect of the tax position included in the completed examination, and (iii) it is remote that the taxing authority would examine or reexamine any aspect of the tax position. Deferred taxes are not provided on translation gains and losses where Duke Energy expects earnings of a foreign operation to be indefinitely reinvested. The Duke Energy Registrants record tax-related interest expense in Interest Expense and interest income and penalties in Other Income and Expenses, net, in the Consolidated Statements of Operations. See Note 24 for further information.
Excise Taxes	Excise Taxes. Certain excise taxes levied by state or local governments are collected by the Duke Energy Registrants from their customers. These taxes, which are required to be paid regardless of the Duke Energy Registrants' ability to collect from the customer, are accounted for on a gross basis. When the Duke Energy Registrants act as an agent, and the tax is not required to be remitted if it is not collected from the customer, the taxes are accounted for on a net basis. The Duke Energy Registrants' excise taxes accounted for on a gross basis and recorded as operating revenues in the Consolidated Statements of Operations were as follows:
Foreign Currency Transaction	Foreign Currency Translation. The local currencies of Duke Energy's foreign operations have been determined to be their functional currencies, except for certain foreign operations whose functional currency has been determined to be the U.S. Dollar, based on an assessment of the economic circumstances of the foreign operation. Assets and liabilities of foreign operations, except for those whose functional currency is the U.S. Dollar, are translated into U.S. Dollars at the exchange rates in effect at period end. Translation adjustments resulting from fluctuations in exchange rates are included as a separate component of AOCI. Revenue and expense accounts of these operations are translated at average exchange rates prevailing during the year. Gains and losses arising from balances and transactions denominated in currencies other than the functional currency are included in the results of operations in the period in which they occur.
Dividend Restrictions And Unappropriated Retained Earnings	Dividend Restrictions and Unappropriated Retained Earnings. Duke Energy does not have any legal, regulatory or other restrictions on paying common stock dividends to shareholders. However, as further described in Note 4, due to conditions established by regulators at the time of the Duke Energy/Cinergy merger in April 2006 and the Duke Energy/Progress Energy merger in 2012, certain wholly owned subsidiaries, including Duke Energy Carolinas, Progress Energy Carolinas, Duke Energy Ohio and Duke Energy Indiana, have restrictions on paying dividends or otherwise advancing funds to Duke Energy. At December 31, 2012 and 2011, an insignificant amount of Duke Energy's consolidated Retained earnings balance represents undistributed earnings of equity method investments.
New Accounting Standards [Policy Text Block]	New Accounting Standards. The following new accounting standards were adopted by the Duke Energy Registrants during the year ended December 31, 2012, and the impact of such adoption, if applicable, has been presented in the accompanying Consolidated Financial Statements: Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC) 220 — Comprehensive Income. In June 2011, the FASB amended the existing requirements for presenting comprehensive income in financial statements primarily to increase the prominence of items reported in other comprehensive income (OCI) and to facilitate the convergence of U.S. GAAP and International Financial Reporting Standards (IFRS). Specifically, the revised guidance eliminates the option previously provided to present components of OCI as part of the statement of changes in stockholders' equity. Accordingly, all non-owner changes in stockholders' equity are required to be presented either in a single continuous statement of comprehensive income or in two separate but consecutive financial statements. For the Duke Energy Registrants, this revised guidance was effective on a retrospective basis for interim and annual periods beginning January 1, 2012. The adoption of this standard changed the presentation of the Duke Energy Registrants' financial statements but did not affect the calculation of net income, comprehensive income or earnings per share. ASC 820 — Fair Value Measurements and Disclosures. In May 2011, the FASB amended existing requirements for measuring fair value and for disclosing information about fair value measurements. This revised guidance results in a consistent definition of fair value, as well as common requirements for measurement and disclosure of fair value information between U.S. GAAP and IFRS. In addition, the amendments set forth enhanced disclosure requirements with respect to recurring Level 3 measurements, nonfinancial assets measured or disclosed at fair value, transfers between levels in the fair value hierarchy, and assets and liabilities disclosed but not recorded at fair value. For the Duke Energy Registrants, the revised fair value measurement guidance was effective on a prospective basis for interim and annual periods beginning January 1, 2012. The adoption of this new guidance did not have a significant impact on the Duke Energy Registrants disclosures or their consolidated results of operations, cash flows, or financial position. The following new accounting standards were adopted by Duke Energy during the year ended December 31, 2011, and the impact of such adoption, if applicable has been presented in the accompanying Consolidated Financial Statements: ASC 605 — Revenue Recognition. In October 2009, the FASB issued new revenue recognition accounting guidance in response to practice concerns related to the accounting for revenue arrangements with multiple deliverables. This new accounting guidance primarily applies to all contractual arrangements in which a vendor will perform multiple revenue generating activities and addresses the unit of accounting for arrangements involving multiple deliverables, as well as how arrangement consideration should be allocated to the separate units of accounting. For the Duke Energy Registrants, the new accounting guidance was effective January 1, 2011, and applied on a prospective basis. This new accounting guidance did not have a material impact to the consolidated results of operations, cash flows or financial position of the Duke Energy Registrants. ASC 805 — Business Combinations. In November 2010, the FASB issued new accounting guidance in response to diversity in the interpretation of pro forma information disclosure requirements for business combinations. The new accounting guidance requires an entity to present pro forma financial information as if a business combination occurred at the beginning of the earliest period presented as well as additional disclosures describing the nature and amount of material, nonrecurring pro forma adjustments. This new accounting guidance was effective January 1, 2011, and has been applied to all business combinations consummated after that date. ASC 820 — Fair Value Measurements and Disclosures. In January 2010, the FASB amended existing fair value measurements and disclosures accounting guidance to clarify certain existing disclosure requirements and to require a number of additional disclosures, including amounts and reasons for significant transfers between the three levels of the fair value hierarchy, and presentation of certain information in the reconciliation of recurring Level 3 measurements on a gross basis. For the Duke Energy Registrants, certain portions of this revised accounting guidance were effective on January 1, 2010, with additional disclosures effective for periods beginning January 1, 2011. The adoption of this accounting guidance resulted in additional disclosure in the notes to the consolidated financial statements but did not have an impact on the Duke Energy Registrants' consolidated results of operations, cash flows or financial position. ASC 350 — Intangibles–Goodwill and Other. In September 2011, the FASB amended existing goodwill impairment testing accounting guidance to provide an entity testing goodwill for impairment with the option of performing a qualitative assessment prior to calculating the fair value of a reporting unit in step one of a goodwill impairment test. Under this revised guidance, a qualitative assessment would require an evaluation of economic, industry, and company-specific considerations. If an entity determines, on a basis of such qualitative factors, that the fair value of a reporting unit is more likely than not less than the carrying value of a reporting unit, the two-step impairment test, as required under pre-existing applicable accounting guidance, would be required. Otherwise, no further impairment testing would be required. The revised goodwill impairment testing accounting guidance is effective for the Duke Energy Registrants' annual and interim goodwill impairment tests performed for fiscal years beginning January 1, 2012, with early adoption of this revised guidance permitted for annual and interim goodwill impairment tests performed as of a date before September 15, 2011. Since annual goodwill impairment tests are performed by Duke Energy as of August 31, the Duke Energy Registrants early adopted this revised accounting guidance during the third quarter of 2011 and applied that guidance to their annual goodwill impairment tests for 2011. The following new accounting standards were adopted by Duke Energy during the year ended December 31, 2010, and the impact of such adoption, if applicable has been presented in the accompanying Consolidated Financial Statements: ASC 860 — Transfers and Servicing. In June 2009, the FASB issued revised accounting guidance for transfers and servicing of financial assets and extinguishment of liabilities, to require additional information about transfers of financial assets, including securitization transactions, as well as additional information about an enterprise's continuing exposure to the risks related to transferred financial assets. This revised accounting guidance eliminated the concept of a Qualifying Special Purpose Entity (QSPE) and required those entities which were not subject to consolidation under previous accounting rules to now be assessed for consolidation. In addition, this accounting guidance clarified and amended the derecognition criteria for transfers of financial assets (including transfers of portions of financial assets) and required additional disclosures about a transferor's continuing involvement in transferred financial assets. For Duke Energy, this revised accounting guidance was effective prospectively for transfers of financial assets occurring on or after January 1, 2010, and early adoption of this statement was prohibited. Since 2002, Duke Energy Ohio, Duke Energy Indiana, and Duke Energy Kentucky have sold, on a revolving basis, nearly all of their accounts receivable and related collections through CRC, a bankruptcy-remote QSPE. The securitization transaction was structured to meet the criteria for sale accounting treatment, and, accordingly, Duke Energy did not consolidate CRC, and the transfers were accounted for as sales. Effective with adoption of this revised accounting guidance and ASC 810-Consolidation, as discussed below, the accounting treatment and/or financial statement presentation of Duke Energy's accounts receivable securitization programs was impacted as Duke Energy began consolidating CRC effective January 1, 2010. Duke Energy Ohio's and Duke Energy Indiana's sales of accounts receivable and related financial statement presentation were not impacted by the adoption of ASC 860. ASC 810 — Consolidations. In June 2009, the FASB amended existing consolidation accounting guidance to eliminate the exemption from consolidation for QSPEs, and clarified, but did not significantly change, the criteria for determining whether an entity meets the definition of a VIE. This revised accounting guidance also required an enterprise to qualitatively assess the determination of the primary beneficiary of a VIE based on whether that enterprise has both the power to direct the activities that most significantly impact the economic performance of a VIE and the obligation to absorb losses or the right to receive benefits of a VIE that could potentially be significant to a VIE. In addition, this revised accounting guidance modified existing accounting guidance to require an ongoing evaluation of a VIE's primary beneficiary and amended the types of events that trigger a reassessment of whether an entity is a VIE. Furthermore, this accounting guidance required enterprises to provide additional disclosures about their involvement with VIEs and any significant changes in their risk exposure due to that involvement. For the Duke Energy Registrants, this accounting guidance was effective beginning on January 1, 2010, and is applicable to all entities in which Duke Energy is involved, including entities previously subject to existing accounting guidance for VIEs, as well as any QSPEs that existed as of the effective date. Effective with adoption of this revised accounting guidance, the accounting treatment and/or financial statement presentation of Duke Energy's accounts receivable securitization programs were impacted as Duke Energy began consolidating CRC effective January 1, 2010. Duke Energy Ohio's and Duke Energy Indiana's sales of accounts receivable and related financial statement presentation were not impacted by the adoption of ASC 810. This revised accounting guidance did not have a significant impact on any of the Duke Energy Registrants' other interests in VIEs. ASC 820 — Fair Value Measurements and Disclosures. In January 2010, the FASB amended existing fair value measurements and disclosures accounting guidance to clarify certain existing disclosure requirements and to require a number of additional disclosures, including amounts and reasons for significant transfers between the three levels of the fair value hierarchy, and presentation of certain information in the reconciliation of recurring Level 3 measurements on a gross basis. For the Duke Energy Registrants, certain portions of this revised accounting guidance were effective on January 1, 2010, with additional disclosures effective for periods beginning January 1, 2011. The initial adoption of this accounting guidance resulted in additional disclosure in the notes to the consolidated financial statements but did not have an impact on the Duke Energy Registrants' consolidated results of operations, cash flows or financial position. The following new Accounting Standards Updates (ASU) have been issued, but have not yet been adopted by Duke Energy, as of December 31, 2012. ASC 210 — Balance Sheet. In December 2011, the FASB issued revised accounting guidance to amend the existing disclosure requirements for offsetting financial assets and liabilities to enhance current disclosures, as well as to improve comparability of balance sheets prepared under U.S. GAAP and IFRS. The revised disclosure guidance affects all companies that have financial instruments and derivative instruments that are either offset in the balance sheet (i.e., presented on a net basis) or subject to an enforceable master netting arrangement and/or similar agreement. The revised guidance requires that certain enhanced quantitative and qualitative disclosures be made with respect to a company's netting arrangements and/or rights of setoff associated with its financial instruments and/or derivative instruments including associated collateral. For the Duke Energy Registrants, the revised disclosure guidance is effective on a retrospective basis for interim and annual periods beginning January 1, 2013. Other than additional disclosures, this revised guidance does not impact the Duke Energy Registrants' consolidated results of operations, cash flows or financial position. ASC 220 — Comprehensive Income. In February 2013, the FASB amended the existing requirements for presenting comprehensive income in financial statements to improve the reporting of reclassifications out of AOCI. The amendments in this Update seek to attain that objective by requiring an entity to report the effect of significant reclassifications out of AOCI on the respective line items in net income if the amount being reclassified is required under U.S. GAAP to be reclassified in its entirety to net income. For other amounts that are not required under U.S. GAAP to be reclassified in their entirety to net income in the same reporting period, an entity is required to cross-reference other disclosures required under U.S. GAAP that provide additional detail about those amounts. This would be the case when a portion of the amount reclassified out of AOCI is reclassified to a balance sheet account (for example, inventory) instead of directly to income or expense in the same reporting period. For the Duke Energy Registrants, this revised guidance is effective on a prospective basis for interim and annual periods beginning January 1, 2013. Other than additional disclosures or a change in the presentation on the statement of comprehensive income, this revised guidance does not impact the Duke Energy Registrants' consolidated results of operations, cash flows or financial position.
Duke Energy Ohio [Member]
Policy Text Block [Line Items]
Organization	Nature of Operations and Basis of Consolidation. Duke Energy Corporation (collectively with its subsidiaries, Duke Energy), is an energy company headquartered in Charlotte, North Carolina. Duke Energy operates in the United States (U.S.) and Latin America primarily through its direct and indirect subsidiaries. Duke Energy's subsidiaries included Duke Energy Carolinas, LLC (Duke Energy Carolinas), Duke Energy Ohio, Inc. (Duke Energy Ohio), which includes Duke Energy Kentucky, Inc. (Duke Energy Kentucky), and Duke Energy Indiana, Inc. (Duke Energy Indiana) prior to the merger with Progress Energy, Inc. (Progress Energy). On July 2, 2012, Duke Energy merged with Progress Energy, with Duke Energy continuing as the surviving corporation, and Progress Energy becoming a subsidiary of Duke Energy. Carolina Power & Light Company d/b/a Progress Energy Carolinas, Inc. (Progress Energy Carolinas) and Florida Power Corporation d/b/a Progress Energy Florida, Inc. (Progress Energy Florida), Progress Energy's regulated utility subsidiaries, are now indirect subsidiaries of Duke Energy. Duke Energy's consolidated financial statements include Progress Energy, Progress Energy Carolinas and Progress Energy Florida activity beginning July 2, 2012. See Note 2 for additional information regarding the merger. When discussing Duke Energy's consolidated financial information, it necessarily includes the results of its six separate subsidiary registrants, Duke Energy Carolinas, Progress Energy, Progress Energy Carolinas, Progress Energy Florida, Duke Energy Ohio and Duke Energy Indiana (collectively referred to as the Subsidiary Registrants), which, along with Duke Energy, are collectively referred to as the Duke Energy Registrants. Progress Energy, Progress Energy Carolinas and Progress Energy Florida (collectively referred to as the Progress Energy Registrants) continue to maintain reporting requirements as SEC registrants. In accordance with SEC guidance, the Progress Energy Registrants did not reflect the impacts of acquisition accounting from the merger with Duke Energy, whereby the adjustments of assets and liabilities to fair value and the resultant goodwill would be shown on the financial statements of the Progress Energy Registrants. These adjustments were recorded by Duke Energy. The information in these combined notes relates to each of the Duke Energy Registrants as noted in the Index to the Combined Notes. However, none of the registrants makes any representation as to information related solely to Duke Energy or the subsidiaries of Duke Energy other than itself. As discussed further in Note 3, Duke Energy operates three reportable business segments: U.S. Franchised Electric and Gas (USFE&G), Commercial Power and International Energy. The remainder of Duke Energy's operations is presented as Other. These Consolidated Financial Statements include, after eliminating intercompany transactions and balances, the accounts of the Duke Energy Registrants and all majority-owned subsidiaries where the respective Duke Energy Registrants have control and those variable interest entities (VIEs) where the respective Duke Energy Registrants are the primary beneficiary. These Consolidated Financial Statements also reflect the Duke Energy Registrants' proportionate share of certain generation and transmission facilities. In January 2012, Duke Energy Ohio completed the sale of its 75% ownership of the Vermillion Generating Station (Vermillion); upon the close, Duke Energy Indiana purchased a 62.5% interest in the station. See Note 2 for further discussion. Duke Energy Carolinas, a wholly owned subsidiary of Duke Energy, is an electric utility company that generates, transmits, distributes and sells electricity in North Carolina and South Carolina. Duke Energy Carolinas is subject to the regulatory provisions of the North Carolina Utilities Commission (NCUC), the Public Service Commission of South Carolina (PSCSC), the U.S. Nuclear Regulatory Commission (NRC) and the Federal Energy Regulatory Commission (FERC). Substantially all of Duke Energy Carolinas' operations are regulated and qualify for regulatory accounting treatment. As discussed further in Note 3, Duke Energy Carolinas' operations include one reportable business segment, Franchised Electric. Progress Energy, a wholly owned subsidiary of Duke Energy, is a holding company headquartered in Raleigh, North Carolina, subject to regulation by the FERC. Progress Energy conducts operations through its wholly owned subsidiaries, Progress Energy Carolinas and Progress Energy Florida. As discussed further in Note 3, Progress Energy's operations include one reportable segment, Franchised Electric. Progress Energy Carolinas, an indirect wholly owned subsidiary of Duke Energy, is a regulated public utility primarily engaged in the generation, transmission, distribution and sale of electricity in portions of North Carolina and South Carolina. Progress Energy Carolinas is subject to the regulatory provisions of the NCUC, the PSCSC, the NRC and the FERC. Substantially all of Progress Energy Carolinas' operations are regulated and qualify for regulatory accounting treatment. As discussed further in Note 3, Progress Energy Carolinas' operations include one reportable segment, Franchised Electric. Progress Energy Florida, an indirect wholly owned subsidiary of Duke Energy, is a regulated public utility primarily engaged in the generation, transmission, distribution and sale of electricity in west central Florida. Progress Energy Florida is subject to the regulatory jurisdiction of the Florida Public Service Commission (FPSC), the NRC and the FERC. Substantially all of Progress Energy Florida's operations are regulated and qualify for regulatory accounting treatment. As discussed further in Note 3, Progress Energy Florida's operations include one reportable segment, Franchised Electric. Duke Energy Ohio, an indirect wholly owned subsidiary of Duke Energy, is a combination electric and gas public utility that provides service in the southwestern portion of Ohio and in northern Kentucky through its wholly owned subsidiary, Duke Energy Kentucky, as well as electric generation in parts of Ohio, Illinois and Pennsylvania. Duke Energy Ohio's principal lines of business include generation, transmission and distribution of electricity, the sale of and/or transportation of natural gas, and energy marketing. Duke Energy Ohio conducts competitive auctions for retail electricity supply in Ohio whereby the energy price is recovered from retail customers. Duke Energy Kentucky's principal lines of business include generation, transmission and distribution of electricity, as well as the sale of and/or transportation of natural gas. References herein to Duke Energy Ohio include Duke Energy Ohio and its subsidiaries, unless otherwise noted. Duke Energy Ohio is subject to the regulatory provisions of the Public Utilities Commission of Ohio (PUCO), the Kentucky Public Service Commission (KPSC) and the FERC. Duke Energy Ohio applies regulatory accounting treatment to substantially all of the operations in its Franchised Electric and Gas operating segment. Through November 2011, Duke Energy Ohio applied regulatory accounting treatment to certain rate riders associated with retail generation of its Commercial Power operating segment. See Note 3 for further information about Duke Energy Ohio's business segments. Duke Energy Indiana, an indirect wholly owned subsidiary of Duke Energy, is an electric utility that provides service in north central, central, and southern Indiana. Its primary line of business is generation, transmission and distribution of electricity. Duke Energy Indiana is subject to the regulatory provisions of the Indiana Utility Regulatory Commission (IURC) and the FERC. Substantially all of Duke Energy Indiana's operations are regulated and qualify for regulatory accounting treatment. As discussed further in Note 3, Duke Energy Indiana's operations include one reportable business segment, Franchised Electric. Certain prior year amounts have been reclassified to conform to current year presentation. In addition, prior year financial statements and footnote disclosures for the Progress Energy Registrants have been reclassified to conform to Duke Energy's presentation.
Use Of Estimates	Use of Estimates. To conform to generally accepted accounting principles (GAAP) in the U.S., management makes estimates and assumptions that affect the amounts reported in the Consolidated Financial Statements and Notes. Although these estimates are based on management's best available information at the time, actual results could differ.
Cost-Based Regulation	Cost-Based Regulation. The Duke Energy Registrants account for their regulated operations in accordance with applicable regulatory accounting guidance. The economic effects of regulation can result in a regulated company recording assets for costs that have been or are expected to be approved for recovery from customers in a future period or recording liabilities for amounts that are expected to be returned to customers in the rate-setting process in a period different from the period in which the amounts would be recorded by an unregulated enterprise. Accordingly, the Duke Energy Registrants record assets and liabilities that result from the regulated ratemaking process that would not be recorded under GAAP for nonregulated entities. Regulatory assets and liabilities are amortized consistent with the treatment of the related cost in the ratemaking process. Management continually assesses whether regulatory assets are probable of future recovery by considering factors such as applicable regulatory changes, recent rate orders applicable to other regulated entities and the status of any pending or potential deregulation legislation. Additionally, management continually assesses whether any regulatory liabilities have been incurred. Based on this continual assessment, management believes the existing regulatory assets are probable of recovery and that no regulatory liabilities, other than those recorded, have been incurred. These regulatory assets and liabilities are classified in the Consolidated Balance Sheets as Regulatory assets and Other in Current Assets and as Regulatory liabilities and Other in Current Liabilities, respectively. The Duke Energy Registrants periodically evaluate the applicability of regulatory accounting treatment by considering factors such as regulatory changes and the impact of competition. If cost-based regulation ends or competition increases, the Duke Energy Registrants may have to reduce their asset balances to reflect a market basis less than cost and write-off the associated regulatory assets and liabilities. If it becomes probable that part of the cost of a plant under construction or a recently completed plant will be disallowed for ratemaking purposes and a reasonable estimate of the amount of the disallowance can be made, that amount is recognized as a loss. In November 2011, in conjunction with the PUCO's approval of its new Electric Security Plan (ESP), Duke Energy Ohio ceased applying regulatory accounting treatment to generation operations within its Commercial Power segment. For further information, see Note 4.
Energy Purchases, Fuel Costs And Fuel Cost Deferrals	Energy Purchases, Fuel Costs and Fuel Cost Deferrals. The Duke Energy Registrants utilize cost-tracking mechanisms, commonly referred to as a fuel adjustment clause, to recover the retail portion of fuel and purchased power. The Duke Energy Registrants defer the related cost through Fuel used in electric generation and purchased power — regulated on the Consolidated Statement of Operations, unless a regulatory requirement exists for deferral through Operating Revenues. Fuel used in electric generation and purchased power — regulated includes fuel, purchased power and recoverable costs that are deferred through fuel clauses established by the Subsidiary Registrants' regulators. These clauses allow the Subsidiary Registrants to recover fuel costs, fuel-related costs and portions of purchased power costs through surcharges on customer rates. The Subsidiary Registrants record any under-recovery or over-recovery resulting from the differences between estimated and actual costs as a regulatory asset or regulatory liability until billed or refunded to customers, at which point the differences are adjusted through revenues. Indiana law limits the amount of fuel costs that Duke Energy Indiana can recover to an amount that will not result in earning a return in excess of that allowed by the IURC. As discussed in Note 4, beginning January 1, 2012, Duke Energy Ohio procures energy for its retail customers through a third-party auction. Purchases of energy through the auction process are a pass-through of costs for Duke Energy Ohio, with no affect on earnings. Subsequent to December 31, 2011, Duke Energy Ohio's generation assets are no longer dedicated to retail customers and, accordingly, Duke Energy Ohio can no longer recover their generation assets' energy purchases and fuel costs from regulated customers.
Cash and Cash Equivalents	Cash and Cash Equivalents. All highly liquid investments with maturities of three months or less at the date of acquisition are considered cash equivalents. At December 31, 2012, Duke Energy had cash and cash equivalents of $1,424 million, of which $731 million is held in foreign jurisdictions and is forecasted to be used to fund international operations and investments
Restricted Cash	Restricted Cash. The Duke Energy Registrants have restricted cash related primarily to collateral assets, escrow deposits, and restricted cash of VIEs. Restricted cash balances are reflected in Other within Current Assets and in Other within Investments and Other Assets on the Consolidated Balance Sheets.
Inventory	Inventory. Inventory is comprised of amounts presented in the tables below and is recorded primarily using the average cost method. Inventory related to the Duke Energy Registrants' regulated operations is valued at historical cost consistent with ratemaking treatment. Materials and supplies are recorded as inventory when purchased and subsequently charged to expense or capitalized to property, plant and equipment when installed. Reserves are established for excess and obsolete inventory. Inventory related to the Duke Energy Registrants' nonregulated operations is valued at the lower of cost or market. The following tables present the Duke Energy Registrants' inventory. Duke Energy Ohio has agreements with a third party through which title of natural gas inventory purchased by Duke Energy Ohio is transferred to a third party. Under the agreements, the gas inventory is stored and managed for Duke Energy Ohio and is delivered on demand. As a result of the agreements, the combined natural gas inventory of approximately $44 million and $50 million being held by a third party as of December 31, 2012, and December 31, 2011, respectively, was classified as Other within Current Assets on the Consolidated Balance Sheets.
Investments In Debt And Equity Securities	Investments in Debt and Equity Securities. The Duke Energy Registrants classify investments into two categories — trading and available-for-sale. Trading securities are reported at fair value in the Consolidated Balance Sheets with net realized and unrealized gains and losses included in earnings each period. Available-for-sale securities are also reported at fair value on the Consolidated Balance Sheets with unrealized gains and losses included in Accumulated Other Comprehensive Income (AOCI) or as a regulatory asset or liability, unless it is determined that the carrying value of an investment is other-than-temporarily impaired. Other-than-temporary impairments related to equity securities and the credit loss portion of debt securities are included in earnings, unless deferred in accordance with regulatory accounting treatment. Investments in debt and equity securities are classified as either short-term investments or long-term investments based on management's intent and ability to sell these securities, taking into consideration illiquidity factors in the current markets with respect to certain investments that have historically provided for a high degree of liquidity, such as investments in auction rate debt securities. See Note 17 for further information on the investments in debt and equity securities, including investments held in the nuclear decommissioning trust funds (NDTF).
Goodwill	Goodwill. Duke Energy and Duke Energy Ohio perform annual goodwill impairment tests as of August 31 each year and update these tests between annual tests if events or circumstances occur that would more likely than not reduce the fair value of a reporting unit below its carrying value. In 2012, Progress Energy changed its goodwill impairment testing date from October 31 to August 31. The change in the goodwill impairment test date is preferable as it better aligns the annual goodwill impairment testing procedures with the testing procedures of Duke Energy. The change in accounting principle did not accelerate, delay, avoid, or cause a goodwill impairment charge. Neither the change in the goodwill impairment testing date nor the merger resulted in any changes to the Progress Energy reporting units. Due to significant judgments and estimates that are utilized in a goodwill impairment analysis, Progress Energy determined it was impracticable to objectively determine, without the use of hindsight, projected cash flows and related valuation estimates as of each August 31, for periods prior to August 31, 2012. As such, the change in the annual goodwill impairment testing date was prospectively applied from August 31, 2012. Duke Energy, Progress Energy and Duke Energy Ohio perform the annual review for goodwill impairment at the reporting unit level, which Duke Energy and Progress Energy have determined to be an operating segment or one level below and which Duke Energy Ohio has determined to be an operating segment. The annual goodwill impairment test may first consider qualitative factors to determine whether it is more likely than not (i.e. greater than 50 percent chance) that the fair value of a reporting unit is less than its book value. This is sometimes referred to as “step zero” and is an optional step in the annual goodwill impairment analysis (see further discussion as discussed in “New Accounting Standards” below). If the results of qualitative assessments indicate that the fair value of a reporting unit is more likely than not less than the carrying value of the reporting unit, the two-step impairment test is required. Step one of the impairment test involves comparing the fair values of reporting units with their carrying values, including goodwill. If the carrying amount is less than fair value in step one, further testing of goodwill is not performed. If the carrying amount of a reporting unit exceeds the reporting unit's fair value, step two must be performed to determine the amount, if any, of the goodwill impairment loss. Step two of the goodwill impairment test involves comparing the implied fair value of the reporting unit's goodwill against the carrying value of the goodwill. Under step two, determining the implied fair value of goodwill requires the valuation of a reporting unit's identifiable tangible and intangible assets and liabilities as if the reporting unit had been acquired in a business combination on the testing date. The difference between the fair value of the entire reporting unit as determined in step one and the net fair value of all identifiable assets and liabilities represents the implied fair value of goodwill. The goodwill impairment charge, if any, would be the excess of the carrying amount of goodwill over the implied fair value of goodwill upon the completion of step two. As a result of the Progress Energy merger, Duke Energy, Progress Energy and Duke Energy Ohio performed step one of the goodwill impairment test as of August 31, 2012, and concluded the fair value of the reporting units exceeded their respective carrying values, and thus, did not record any impairment charges. In 2011, Duke Energy and Duke Energy Ohio performed the qualitative assessments under step zero and concluded that it was more likely than not the fair value of each reporting unit exceeded its carrying value. In 2011, Progress Energy performed step one of the goodwill impairment test, which indicated the carrying amounts of goodwill were not impaired. In 2010, Duke Energy, Progress Energy and Duke Energy Ohio used the two-step process to test goodwill for impairment, which resulted in impairments recorded by Duke Energy and Duke Energy Ohio. See Note 12 for further information.
Long-Lived Asset Impairments	Long-Lived Asset Impairments. The Duke Energy Registrants evaluate whether long-lived assets, excluding goodwill, have been impaired when circumstances indicate the carrying value of those assets may not be recoverable. For such long-lived assets, an impairment exists when its carrying value exceeds the sum of estimates of the undiscounted cash flows expected to result from the use and eventual disposition of the asset. When alternative courses of action to recover the carrying amount of a long-lived asset are under consideration, a probability-weighted approach is used for developing estimates of future undiscounted cash flows. If the carrying value of the long-lived asset is not recoverable based on these estimated future undiscounted cash flows, the impairment loss is measured as the excess of the carrying value of the asset over its fair value, such that the asset's carrying value is adjusted to its estimated fair value. Management assesses the fair value of long-lived assets using commonly accepted techniques, and may use more than one source. Sources to determine fair value include, but are not limited to, recent third party comparable sales, internally developed discounted cash flow analysis and analysis from outside advisors. Significant changes in market conditions resulting from events such as, among others, changes in commodity prices or the condition of an asset, or a change in management's intent to utilize the asset are generally viewed by management as triggering events to re-assess the cash flows related to the long-lived assets. See Note 12 for further information.
Property, Plant and Equipment	Property, Plant and Equipment. Property, plant and equipment are stated at the lower of historical cost less accumulated depreciation or fair value, if impaired. The Duke Energy Registrants capitalize all construction-related direct labor and material costs, as well as indirect construction costs. Indirect costs include general engineering, taxes and the allowance for funds used during construction (AFUDC). See “AFUDC and Interest Capitalized,” below for additional information. The cost of renewals and betterments that extend the useful life of property, plant and equipment are also capitalized. The cost of repairs, replacements and major maintenance projects, which do not extend the useful life or increase the expected output of the asset, are expensed as incurred. Depreciation is generally computed over the estimated useful life of the asset using the composite straight-line method. For regulated operations, depreciation studies are conducted periodically to update the composite rates and are approved by the various state commissions. The composite weighted-average depreciation rates, excluding nuclear fuel, for each of the Duke Energy Registrants are included in the following table: When the Duke Energy Registrants retire regulated property, plant and equipment under what is considered a normal retirement, the original cost plus the cost of retirement, less salvage value, is charged to accumulated depreciation, consistent with regulated rate-making practices. When it becomes probable that a regulated generation asset will be retired substantially in advance of its original expected useful life or is abandoned, the cost of the asset and the corresponding accumulated depreciation is removed from Cost and Accumulated depreciation and amortization within Property, Plant and Equipment on the Consolidated Balance Sheets and a separate asset is recognized. If the plant is still in operation, the amount is classified as Generation facilities to be retired, net on the Consolidated Balance Sheets. If the plant is no longer operating, then a regulatory asset is recognized. The carrying value of the asset is based on historical cost if the Duke Energy Registrants are allowed to recover the remaining net book value and a full return on the asset. If the Duke Energy Registrants do not expect to recover the full remaining cost and a full return, the carrying value of the asset is based on the lower of cost or the present value of the future revenues expected to be provided to recover the allowable costs discounted at the Duke Energy Registrants' incremental borrowing rate. An impairment is recognized if the net book value of the asset exceeds the present value of the future revenues to be recovered in rates. When the Duke Energy Registrants sell entire regulated operating units, or retire or sell nonregulated properties, the original cost is removed from property and the related accumulated depreciation and amortization balances are reduced. Any gain or loss is recorded in earnings, unless otherwise required by the applicable regulatory body. See Note 10 for further information on the components and estimated useful lives of Duke Energy's property, plant and equipment.
AFUDC And Interest Capitalized	AFUDC and Interest Capitalized. In accordance with applicable regulatory accounting guidance, the Duke Energy Registrants record AFUDC, which represents the estimated debt and equity costs of capital funds necessary to finance the construction of new regulated facilities. The equity component of AFUDC is a non-cash amount within the Consolidated Statements of Operations. AFUDC is capitalized as a component of the cost of property, plant and equipment, with an offsetting credit to Other income and expenses, net on the Consolidated Statements of Operations for the equity component and as an offset to Interest Expense on the Consolidated Statements of Operations for the debt component. After construction is completed, the Duke Energy Registrants are permitted to recover these costs through inclusion in the rate base and the corresponding depreciation expense or nuclear fuel expense. AFUDC equity is a permanent difference item for income tax purposes, thus reducing the Duke Energy Registrants' effective tax rate during the construction phase in which AFUDC equity is being recorded. The effective tax rate is subsequently increased in future periods when the completed property, plant and equipment are placed in service and depreciation of the AFUDC equity commences. See Note 24 for information related to the impacts of AFUDC equity on the Duke Energy Registrants' effective tax rate. For nonregulated operations, interest is capitalized during the construction phase in accordance with the applicable accounting guidance.
Asset Retirement Obligations	Asset Retirement Obligations. The Duke Energy Registrants recognize asset retirement obligations for legal obligations associated with the retirement of long-lived assets that result from the acquisition, construction, development and/or normal use of the asset, and for conditional asset retirement obligations. The term conditional asset retirement obligation refers to a legal obligation to perform an asset retirement activity in which the timing and (or) method of settlement are conditional on a future event that may or may not be within the control of the entity. The obligation to perform the asset retirement activity is unconditional even though uncertainty exists about the timing and (or) method of settlement. Thus, the timing and (or) method of settlement may be conditional on a future event. When recording an asset retirement obligation, the present value of the projected liability is recognized in the period in which it is incurred, if a reasonable estimate of fair value can be made. The liability is then accreted over time by applying an interest method of allocation to the liability. Substantially all accretion is related to regulated operations and is deferred pursuant to regulatory accounting. The present value of the liability is added to the carrying amount of the associated asset and this additional carrying amount is depreciated over the remaining life of the asset. The present value of the initial obligation and subsequent updates are based on discounted cash flows, which include estimates regarding the timing of future cash flows, the selection of discount rates and cost escalation rates, among other factors. These underlying assumptions and estimates are made as of a point in time and are subject to change. The obligations for nuclear decommissioning are based on site-specific cost studies. Duke Energy Carolinas and Progress Energy Carolinas assume prompt dismantlement of the nuclear facilities, which reflects dismantling the site after operations are ceased. Progress Energy Florida assumes the nuclear facility will be placed into a safe storage configuration until the eventual dismantling of the site begins in approximately 40-60 years. The nuclear decommissioning asset retirement obligation also assumes Duke Energy Carolinas, Progress Energy Carolinas and Progress Energy Florida will store spent fuel on site until such time that it can be transferred to a U.S. Department of Energy (DOE) facility. See Note 9 for further information.
Unbilled Revenue	Revenue Recognition and Unbilled Revenue. Revenues on sales of electricity and gas are recognized when either the service is provided or the product is delivered. Unbilled retail revenues are estimated by applying average revenue per kilowatt-hour (kWh) or per thousand cubic feet (Mcf) for all customer classes to the number of estimated kWh or Mcf delivered but not billed. Unbilled wholesale energy revenues are calculated by applying the contractual rate per megawatt-hour (MWh) to the number of estimated MWh delivered but not yet billed. Unbilled wholesale demand revenues are calculated by applying the contractual rate per megawatt (MW) to the MW volume delivered but not yet billed. The amount of unbilled revenues can vary significantly from period to period as a result of numerous factors, including seasonality, weather, customer usage patterns and customer mix. The Duke Energy Registrants had unbilled revenues within Receivables and within Restricted receivables of variable interest entities on their respective Consolidated Balance Sheets as shown in the table below. Additionally, Duke Energy Ohio and Duke Energy Indiana sell, on a revolving basis, nearly all of their retail and wholesale accounts receivable to Cinergy Receivables Company, LLC (CRC). These transfers meet sales/derecognition criteria and, therefore, Duke Energy Ohio and Duke Energy Indiana account for the transfers of receivables to Cinergy Receivables as sales. Accordingly, the receivables sold are not reflected on the Consolidated Balance Sheets of Duke Energy Ohio and Duke Energy Indiana. See Note 18 for further information. Receivables for unbilled revenues related to retail and wholesale accounts receivable at Duke Energy Ohio and Duke Energy Indiana included in the sales of accounts receivable to CRC were as shown in the table below.
Accounting For Risk Management, Hedging Activities And Financial Instruments	Accounting for Risk Management, Hedging Activities and Financial Instruments. The Duke Energy Registrants may use a number of different derivative and non-derivative instruments in connection with their commodity price, interest rate and foreign currency risk management activities, including swaps, futures, forwards and options. All derivative instruments except those that qualify for the normal purchase/normal sale (NPNS) exception within the accounting guidance for derivatives are recorded on the Consolidated Balance Sheets at their fair value. The effective portion of the change in the fair value of derivative instruments designated as cash flow hedges is recorded in AOCI. The effective portion of the change in the fair value of a fair value hedge is offset in net income by changes in the hedged item. The Duke Energy Registrants may designate qualifying derivative instruments as either cash flow hedges or fair value hedges, while others either have not been designated as hedges or do not qualify as a hedge (hereinafter referred to as undesignated contracts). For all contracts accounted for as a hedge, the Duke Energy Registrants prepare formal documentation of the hedge in accordance with the accounting guidance for derivatives. In addition, at inception and at least every three months thereafter, the Duke Energy Registrants formally assess whether the hedge contract is highly effective in offsetting changes in cash flows or fair values of hedged items. The Duke Energy Registrants document hedging activity by transaction type and risk management strategy. See Note 15 for further information.
Captive Insurance Reserves	Captive Insurance Reserves. Duke Energy has captive insurance subsidiaries that provide coverage, on an indemnity basis, to the Subsidiary Registrants as well as certain third parties, on a limited basis, for various business risks and losses, such as property, business interruption, workers' compensation and general liability. Liabilities include provisions for estimated losses incurred but not yet reported (IBNR), as well as provisions for known claims which have been estimated on a claims-incurred basis. IBNR reserve estimates involve the use of assumptions and are primarily based upon historical loss experience, industry data and other actuarial assumptions. Reserve estimates are adjusted in future periods as actual losses differ from historical experience. Duke Energy, through its captive insurance entities, also has reinsurance coverage with third parties, which provides reimbursement for certain losses above a per occurrence and/or aggregate retention. Duke Energy recognizes a reinsurance receivable for recovery of incurred losses under its captive's reinsurance coverage once realization of the receivable is deemed probable.
Unamortized Debt Premium, Discount And Expense	Unamortized Debt Premium, Discount and Expense. Premiums, discounts and expenses incurred with the issuance of outstanding long-term debt are amortized over the terms of the debt issues. Any call premiums or unamortized expenses associated with refinancing higher-cost debt obligations used to finance regulated assets and operations are amortized consistent with regulatory treatment of those items, where appropriate. The amortization expense is recorded as a component of Interest Expense in the Consolidated Statements of Operations and is reflected as Depreciation, amortization and accretion within Net cash provided by operating activities on the Consolidated Statements of Cash Flows.
Loss Contingencies And Environmental Liabilities	Loss Contingencies and Environmental Liabilities. The Duke Energy Registrants are involved in certain legal and environmental matters that arise in the normal course of business. Contingent losses are recorded when it is determined that it is probable that a loss has occurred and the amount of the loss can be reasonably estimated. When a range of the probable loss exists and no amount within the range is a better estimate than any other amount, the Duke Energy Registrants record a loss contingency at the minimum amount in the range. Unless otherwise required by GAAP, legal fees are expensed as incurred. Environmental liabilities are recorded on an undiscounted basis when the necessity for environmental remediation becomes probable and the costs can be reasonably estimated, or when other potential environmental liabilities are reasonably estimable and probable. The Duke Energy Registrants expense environmental expenditures related to conditions caused by past operations that do not generate current or future revenues. Certain environmental expenses receive regulatory accounting treatment, under which the expenses are recorded as regulatory assets. Environmental expenditures related to operations that generate current or future revenues are expensed or capitalized, as appropriate. See Note 5 for further information.
Pension And Other Post-Retirement Benefit Plans	Pension and Other Post-Retirement Benefit Plans. Duke Energy maintains qualified, non-qualified and other post-retirement benefit plans. Eligible employees of the Subsidiary Registrants participate in the respective Duke Energy or Progress Energy qualified, non-qualified and other post-retirement benefit plans and are allocated their proportionate share of benefit costs. See Note 23 for information related to Duke Energy's benefit plans, including certain accounting policies associated with these plans.
Severance And Special Termination Benefits	Severance and Special Termination Benefits. Duke Energy has an ongoing severance plan under which, in general, the longer a terminated employee worked prior to termination the greater the amount of severance benefits. The Duke Energy Registrants record a liability for involuntary severance once an involuntary severance plan is committed to by management, or sooner, if involuntary severances are probable and the related severance benefits can be reasonably estimated. For involuntary severance benefits that are incremental to its ongoing severance plan benefits, Duke Energy measures the obligation and records the expense at its fair value at the communication date if there are no future service requirements, or, if future service is required to receive the termination benefit, ratably over the service period. From time to time, Duke Energy offers special termination benefits under voluntary severance programs. Special termination benefits are measured upon employee acceptance and recorded immediately absent a significant retention period. If a significant retention period exists, the cost of the special termination benefits are recorded ratably over the remaining service periods of the affected employees. Employee acceptance of voluntary severance benefits is determined by management based on the facts and circumstances of the special termination benefits being offered. See Note 21 for further information.
Guarantees	Guarantees. Upon issuance or modification of a guarantee, the Duke Energy Registrants recognize a liability at the time of issuance or material modification for the estimated fair value of the obligation it assumes under that guarantee, if any. Fair value is estimated using a probability-weighted approach. The Duke Energy Registrants reduce the obligation over the term of the guarantee or related contract in a systematic and rational method as risk is reduced under the obligation. Any additional contingent loss for guarantee contracts subsequent to the initial recognition of a liability in accordance with applicable accounting guidance is accounted for and recognized at the time a loss is probable and the amount of the loss can be reasonably estimated. The Duke Energy Registrants have entered into various indemnification agreements related to purchase and sale agreements and other types of contractual agreements with vendors and other third parties. These agreements typically cover environmental, tax, litigation and other matters, as well as breaches of representations, warranties and covenants. Typically, claims may be made by third parties for various periods of time, depending on the nature of the claim. Potential exposure under these indemnification agreements can range from a specified to an unlimited dollar amount, depending on the nature of the claim and the particular transaction. See Note 7 for further information.
Stock-based Compensation	Stock-Based Compensation. Stock-based compensation represents the cost related to stock-based awards granted to employees. Duke Energy recognizes stock-based compensation based upon the estimated fair value of the awards, net of estimated forfeitures. The recognition period for these costs begin at either the applicable service inception date or grant date and continues throughout the requisite service period, or for certain share-based awards until the employee becomes retirement eligible, if earlier. Share-based awards, including stock options, but not performance shares, granted to employees that are already retirement eligible are deemed to have vested immediately upon issuance, and, therefore, compensation cost for those awards is recognized on the date such awards are granted. See Note 22 for further information.
Accounting For Purchases And Sales Of Emission Allowances	Accounting For Purchases and Sales of Emission Allowances. Emission allowances are issued by the Environmental Protection Agency (EPA) at zero cost and permit the holder of the allowance to emit certain gaseous by-products of fossil fuel combustion, including sulfur dioxide (SO2) and nitrogen oxide (NOx). Allowances may also be bought and sold via third-party transactions. Allowances allocated to or acquired by the Duke Energy Registrants are held primarily for consumption. Emission allowances at cost are included in Intangibles, net on the Consolidated Balance Sheets and the Duke Energy Registrants recognize expense as the allowances are consumed or sold. Gains or losses on sales of emission allowances by regulated businesses that do not provide for direct recovery through a cost-tracking mechanism and by nonregulated businesses are presented in Gains on Sales of Other Assets and Other, net, in the Consolidated Statements of Operations. For regulated businesses that provide for direct recovery of emission allowances, any gain or loss on sales of recoverable emission allowances are included in the rate structure of the regulated entity and are deferred as a regulatory asset or liability. Future rates charged to retail customers are impacted by any gain or loss on sales of recoverable emission allowances. Purchases and sales of emission allowances are presented gross as investing activities on the Consolidated Statements of Cash Flows. See Note 12 for discussion regarding the impairment of the carrying value of certain emission allowances in 2011.
Income Taxes	Income Taxes. Duke Energy and its subsidiaries file a consolidated federal income tax return and other state and foreign jurisdictional returns as required. Deferred income taxes have been provided for temporary differences between the GAAP and tax carrying amounts of assets and liabilities. These differences create taxable or tax-deductible amounts for future periods. Investment tax credits (ITC) associated with regulated operations are deferred and are amortized as a reduction of income tax expense over the estimated useful lives of the related properties. The Subsidiary Registrants entered into a tax sharing agreement with Duke Energy, where the separate return method is used to allocate tax expenses and benefits to the subsidiaries whose investments or results of operations provide these tax expenses or benefits. The accounting for income taxes essentially represents the income taxes that the Subsidiary Registrants would incur if the Subsidiary Registrants were a separate company filing its own federal tax return as a C-Corporation. The Duke Energy Registrants record unrecognized tax benefits for positions taken or expected to be taken on tax returns, including the decision to exclude certain income or transactions from a return, when a more-likely-than-not threshold is met for a tax position and management believes that the position will be sustained upon examination by the taxing authorities. Management evaluates each position based solely on the technical merits and facts and circumstances of the position, assuming the position will be examined by a taxing authority having full knowledge of all relevant information. The Duke Energy Registrants record the largest amount of the unrecognized tax benefit that is greater than 50% likely of being realized upon settlement or effective settlement. Management considers a tax position effectively settled for the purpose of recognizing previously unrecognized tax benefits when the following conditions exist: (i) the taxing authority has completed its examination procedures, including all appeals and administrative reviews that the taxing authority is required and expected to perform for the tax positions, (ii) the Duke Energy Registrants do not intend to appeal or litigate any aspect of the tax position included in the completed examination, and (iii) it is remote that the taxing authority would examine or reexamine any aspect of the tax position. Deferred taxes are not provided on translation gains and losses where Duke Energy expects earnings of a foreign operation to be indefinitely reinvested. The Duke Energy Registrants record tax-related interest expense in Interest Expense and interest income and penalties in Other Income and Expenses, net, in the Consolidated Statements of Operations. See Note 24 for further information.
Excise Taxes	Excise Taxes. Certain excise taxes levied by state or local governments are collected by the Duke Energy Registrants from their customers. These taxes, which are required to be paid regardless of the Duke Energy Registrants' ability to collect from the customer, are accounted for on a gross basis. When the Duke Energy Registrants act as an agent, and the tax is not required to be remitted if it is not collected from the customer, the taxes are accounted for on a net basis. The Duke Energy Registrants' excise taxes accounted for on a gross basis and recorded as operating revenues in the Consolidated Statements of Operations were as follows:
Foreign Currency Transaction	Foreign Currency Translation. The local currencies of Duke Energy's foreign operations have been determined to be their functional currencies, except for certain foreign operations whose functional currency has been determined to be the U.S. Dollar, based on an assessment of the economic circumstances of the foreign operation. Assets and liabilities of foreign operations, except for those whose functional currency is the U.S. Dollar, are translated into U.S. Dollars at the exchange rates in effect at period end. Translation adjustments resulting from fluctuations in exchange rates are included as a separate component of AOCI. Revenue and expense accounts of these operations are translated at average exchange rates prevailing during the year. Gains and losses arising from balances and transactions denominated in currencies other than the functional currency are included in the results of operations in the period in which they occur.
Dividend Restrictions And Unappropriated Retained Earnings	Dividend Restrictions and Unappropriated Retained Earnings. Duke Energy does not have any legal, regulatory or other restrictions on paying common stock dividends to shareholders. However, as further described in Note 4, due to conditions established by regulators at the time of the Duke Energy/Cinergy merger in April 2006 and the Duke Energy/Progress Energy merger in 2012, certain wholly owned subsidiaries, including Duke Energy Carolinas, Progress Energy Carolinas, Duke Energy Ohio and Duke Energy Indiana, have restrictions on paying dividends or otherwise advancing funds to Duke Energy. At December 31, 2012 and 2011, an insignificant amount of Duke Energy's consolidated Retained earnings balance represents undistributed earnings of equity method investments.
New Accounting Standards [Policy Text Block]	New Accounting Standards. The following new accounting standards were adopted by the Duke Energy Registrants during the year ended December 31, 2012, and the impact of such adoption, if applicable, has been presented in the accompanying Consolidated Financial Statements: Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC) 220 — Comprehensive Income. In June 2011, the FASB amended the existing requirements for presenting comprehensive income in financial statements primarily to increase the prominence of items reported in other comprehensive income (OCI) and to facilitate the convergence of U.S. GAAP and International Financial Reporting Standards (IFRS). Specifically, the revised guidance eliminates the option previously provided to present components of OCI as part of the statement of changes in stockholders' equity. Accordingly, all non-owner changes in stockholders' equity are required to be presented either in a single continuous statement of comprehensive income or in two separate but consecutive financial statements. For the Duke Energy Registrants, this revised guidance was effective on a retrospective basis for interim and annual periods beginning January 1, 2012. The adoption of this standard changed the presentation of the Duke Energy Registrants' financial statements but did not affect the calculation of net income, comprehensive income or earnings per share. ASC 820 — Fair Value Measurements and Disclosures. In May 2011, the FASB amended existing requirements for measuring fair value and for disclosing information about fair value measurements. This revised guidance results in a consistent definition of fair value, as well as common requirements for measurement and disclosure of fair value information between U.S. GAAP and IFRS. In addition, the amendments set forth enhanced disclosure requirements with respect to recurring Level 3 measurements, nonfinancial assets measured or disclosed at fair value, transfers between levels in the fair value hierarchy, and assets and liabilities disclosed but not recorded at fair value. For the Duke Energy Registrants, the revised fair value measurement guidance was effective on a prospective basis for interim and annual periods beginning January 1, 2012. The adoption of this new guidance did not have a significant impact on the Duke Energy Registrants disclosures or their consolidated results of operations, cash flows, or financial position. The following new accounting standards were adopted by Duke Energy during the year ended December 31, 2011, and the impact of such adoption, if applicable has been presented in the accompanying Consolidated Financial Statements: ASC 605 — Revenue Recognition. In October 2009, the FASB issued new revenue recognition accounting guidance in response to practice concerns related to the accounting for revenue arrangements with multiple deliverables. This new accounting guidance primarily applies to all contractual arrangements in which a vendor will perform multiple revenue generating activities and addresses the unit of accounting for arrangements involving multiple deliverables, as well as how arrangement consideration should be allocated to the separate units of accounting. For the Duke Energy Registrants, the new accounting guidance was effective January 1, 2011, and applied on a prospective basis. This new accounting guidance did not have a material impact to the consolidated results of operations, cash flows or financial position of the Duke Energy Registrants. ASC 805 — Business Combinations. In November 2010, the FASB issued new accounting guidance in response to diversity in the interpretation of pro forma information disclosure requirements for business combinations. The new accounting guidance requires an entity to present pro forma financial information as if a business combination occurred at the beginning of the earliest period presented as well as additional disclosures describing the nature and amount of material, nonrecurring pro forma adjustments. This new accounting guidance was effective January 1, 2011, and has been applied to all business combinations consummated after that date. ASC 820 — Fair Value Measurements and Disclosures. In January 2010, the FASB amended existing fair value measurements and disclosures accounting guidance to clarify certain existing disclosure requirements and to require a number of additional disclosures, including amounts and reasons for significant transfers between the three levels of the fair value hierarchy, and presentation of certain information in the reconciliation of recurring Level 3 measurements on a gross basis. For the Duke Energy Registrants, certain portions of this revised accounting guidance were effective on January 1, 2010, with additional disclosures effective for periods beginning January 1, 2011. The adoption of this accounting guidance resulted in additional disclosure in the notes to the consolidated financial statements but did not have an impact on the Duke Energy Registrants' consolidated results of operations, cash flows or financial position. ASC 350 — Intangibles–Goodwill and Other. In September 2011, the FASB amended existing goodwill impairment testing accounting guidance to provide an entity testing goodwill for impairment with the option of performing a qualitative assessment prior to calculating the fair value of a reporting unit in step one of a goodwill impairment test. Under this revised guidance, a qualitative assessment would require an evaluation of economic, industry, and company-specific considerations. If an entity determines, on a basis of such qualitative factors, that the fair value of a reporting unit is more likely than not less than the carrying value of a reporting unit, the two-step impairment test, as required under pre-existing applicable accounting guidance, would be required. Otherwise, no further impairment testing would be required. The revised goodwill impairment testing accounting guidance is effective for the Duke Energy Registrants' annual and interim goodwill impairment tests performed for fiscal years beginning January 1, 2012, with early adoption of this revised guidance permitted for annual and interim goodwill impairment tests performed as of a date before September 15, 2011. Since annual goodwill impairment tests are performed by Duke Energy as of August 31, the Duke Energy Registrants early adopted this revised accounting guidance during the third quarter of 2011 and applied that guidance to their annual goodwill impairment tests for 2011. The following new accounting standards were adopted by Duke Energy during the year ended December 31, 2010, and the impact of such adoption, if applicable has been presented in the accompanying Consolidated Financial Statements: ASC 860 — Transfers and Servicing. In June 2009, the FASB issued revised accounting guidance for transfers and servicing of financial assets and extinguishment of liabilities, to require additional information about transfers of financial assets, including securitization transactions, as well as additional information about an enterprise's continuing exposure to the risks related to transferred financial assets. This revised accounting guidance eliminated the concept of a Qualifying Special Purpose Entity (QSPE) and required those entities which were not subject to consolidation under previous accounting rules to now be assessed for consolidation. In addition, this accounting guidance clarified and amended the derecognition criteria for transfers of financial assets (including transfers of portions of financial assets) and required additional disclosures about a transferor's continuing involvement in transferred financial assets. For Duke Energy, this revised accounting guidance was effective prospectively for transfers of financial assets occurring on or after January 1, 2010, and early adoption of this statement was prohibited. Since 2002, Duke Energy Ohio, Duke Energy Indiana, and Duke Energy Kentucky have sold, on a revolving basis, nearly all of their accounts receivable and related collections through CRC, a bankruptcy-remote QSPE. The securitization transaction was structured to meet the criteria for sale accounting treatment, and, accordingly, Duke Energy did not consolidate CRC, and the transfers were accounted for as sales. Effective with adoption of this revised accounting guidance and ASC 810-Consolidation, as discussed below, the accounting treatment and/or financial statement presentation of Duke Energy's accounts receivable securitization programs was impacted as Duke Energy began consolidating CRC effective January 1, 2010. Duke Energy Ohio's and Duke Energy Indiana's sales of accounts receivable and related financial statement presentation were not impacted by the adoption of ASC 860. ASC 810 — Consolidations. In June 2009, the FASB amended existing consolidation accounting guidance to eliminate the exemption from consolidation for QSPEs, and clarified, but did not significantly change, the criteria for determining whether an entity meets the definition of a VIE. This revised accounting guidance also required an enterprise to qualitatively assess the determination of the primary beneficiary of a VIE based on whether that enterprise has both the power to direct the activities that most significantly impact the economic performance of a VIE and the obligation to absorb losses or the right to receive benefits of a VIE that could potentially be significant to a VIE. In addition, this revised accounting guidance modified existing accounting guidance to require an ongoing evaluation of a VIE's primary beneficiary and amended the types of events that trigger a reassessment of whether an entity is a VIE. Furthermore, this accounting guidance required enterprises to provide additional disclosures about their involvement with VIEs and any significant changes in their risk exposure due to that involvement. For the Duke Energy Registrants, this accounting guidance was effective beginning on January 1, 2010, and is applicable to all entities in which Duke Energy is involved, including entities previously subject to existing accounting guidance for VIEs, as well as any QSPEs that existed as of the effective date. Effective with adoption of this revised accounting guidance, the accounting treatment and/or financial statement presentation of Duke Energy's accounts receivable securitization programs were impacted as Duke Energy began consolidating CRC effective January 1, 2010. Duke Energy Ohio's and Duke Energy Indiana's sales of accounts receivable and related financial statement presentation were not impacted by the adoption of ASC 810. This revised accounting guidance did not have a significant impact on any of the Duke Energy Registrants' other interests in VIEs. ASC 820 — Fair Value Measurements and Disclosures. In January 2010, the FASB amended existing fair value measurements and disclosures accounting guidance to clarify certain existing disclosure requirements and to require a number of additional disclosures, including amounts and reasons for significant transfers between the three levels of the fair value hierarchy, and presentation of certain information in the reconciliation of recurring Level 3 measurements on a gross basis. For the Duke Energy Registrants, certain portions of this revised accounting guidance were effective on January 1, 2010, with additional disclosures effective for periods beginning January 1, 2011. The initial adoption of this accounting guidance resulted in additional disclosure in the notes to the consolidated financial statements but did not have an impact on the Duke Energy Registrants' consolidated results of operations, cash flows or financial position. The following new Accounting Standards Updates (ASU) have been issued, but have not yet been adopted by Duke Energy, as of December 31, 2012. ASC 210 — Balance Sheet. In December 2011, the FASB issued revised accounting guidance to amend the existing disclosure requirements for offsetting financial assets and liabilities to enhance current disclosures, as well as to improve comparability of balance sheets prepared under U.S. GAAP and IFRS. The revised disclosure guidance affects all companies that have financial instruments and derivative instruments that are either offset in the balance sheet (i.e., presented on a net basis) or subject to an enforceable master netting arrangement and/or similar agreement. The revised guidance requires that certain enhanced quantitative and qualitative disclosures be made with respect to a company's netting arrangements and/or rights of setoff associated with its financial instruments and/or derivative instruments including associated collateral. For the Duke Energy Registrants, the revised disclosure guidance is effective on a retrospective basis for interim and annual periods beginning January 1, 2013. Other than additional disclosures, this revised guidance does not impact the Duke Energy Registrants' consolidated results of operations, cash flows or financial position. ASC 220 — Comprehensive Income. In February 2013, the FASB amended the existing requirements for presenting comprehensive income in financial statements to improve the reporting of reclassifications out of AOCI. The amendments in this Update seek to attain that objective by requiring an entity to report the effect of significant reclassifications out of AOCI on the respective line items in net income if the amount being reclassified is required under U.S. GAAP to be reclassified in its entirety to net income. For other amounts that are not required under U.S. GAAP to be reclassified in their entirety to net income in the same reporting period, an entity is required to cross-reference other disclosures required under U.S. GAAP that provide additional detail about those amounts. This would be the case when a portion of the amount reclassified out of AOCI is reclassified to a balance sheet account (for example, inventory) instead of directly to income or expense in the same reporting period. For the Duke Energy Registrants, this revised guidance is effective on a prospective basis for interim and annual periods beginning January 1, 2013. Other than additional disclosures or a change in the presentation on the statement of comprehensive income, this revised guidance does not impact the Duke Energy Registrants' consolidated results of operations, cash flows or financial position.
Duke Energy Indiana [Member]
Policy Text Block [Line Items]
Organization	Nature of Operations and Basis of Consolidation. Duke Energy Corporation (collectively with its subsidiaries, Duke Energy), is an energy company headquartered in Charlotte, North Carolina. Duke Energy operates in the United States (U.S.) and Latin America primarily through its direct and indirect subsidiaries. Duke Energy's subsidiaries included Duke Energy Carolinas, LLC (Duke Energy Carolinas), Duke Energy Ohio, Inc. (Duke Energy Ohio), which includes Duke Energy Kentucky, Inc. (Duke Energy Kentucky), and Duke Energy Indiana, Inc. (Duke Energy Indiana) prior to the merger with Progress Energy, Inc. (Progress Energy). On July 2, 2012, Duke Energy merged with Progress Energy, with Duke Energy continuing as the surviving corporation, and Progress Energy becoming a subsidiary of Duke Energy. Carolina Power & Light Company d/b/a Progress Energy Carolinas, Inc. (Progress Energy Carolinas) and Florida Power Corporation d/b/a Progress Energy Florida, Inc. (Progress Energy Florida), Progress Energy's regulated utility subsidiaries, are now indirect subsidiaries of Duke Energy. Duke Energy's consolidated financial statements include Progress Energy, Progress Energy Carolinas and Progress Energy Florida activity beginning July 2, 2012. See Note 2 for additional information regarding the merger. When discussing Duke Energy's consolidated financial information, it necessarily includes the results of its six separate subsidiary registrants, Duke Energy Carolinas, Progress Energy, Progress Energy Carolinas, Progress Energy Florida, Duke Energy Ohio and Duke Energy Indiana (collectively referred to as the Subsidiary Registrants), which, along with Duke Energy, are collectively referred to as the Duke Energy Registrants. Progress Energy, Progress Energy Carolinas and Progress Energy Florida (collectively referred to as the Progress Energy Registrants) continue to maintain reporting requirements as SEC registrants. In accordance with SEC guidance, the Progress Energy Registrants did not reflect the impacts of acquisition accounting from the merger with Duke Energy, whereby the adjustments of assets and liabilities to fair value and the resultant goodwill would be shown on the financial statements of the Progress Energy Registrants. These adjustments were recorded by Duke Energy. The information in these combined notes relates to each of the Duke Energy Registrants as noted in the Index to the Combined Notes. However, none of the registrants makes any representation as to information related solely to Duke Energy or the subsidiaries of Duke Energy other than itself. As discussed further in Note 3, Duke Energy operates three reportable business segments: U.S. Franchised Electric and Gas (USFE&G), Commercial Power and International Energy. The remainder of Duke Energy's operations is presented as Other. These Consolidated Financial Statements include, after eliminating intercompany transactions and balances, the accounts of the Duke Energy Registrants and all majority-owned subsidiaries where the respective Duke Energy Registrants have control and those variable interest entities (VIEs) where the respective Duke Energy Registrants are the primary beneficiary. These Consolidated Financial Statements also reflect the Duke Energy Registrants' proportionate share of certain generation and transmission facilities. In January 2012, Duke Energy Ohio completed the sale of its 75% ownership of the Vermillion Generating Station (Vermillion); upon the close, Duke Energy Indiana purchased a 62.5% interest in the station. See Note 2 for further discussion. Duke Energy Carolinas, a wholly owned subsidiary of Duke Energy, is an electric utility company that generates, transmits, distributes and sells electricity in North Carolina and South Carolina. Duke Energy Carolinas is subject to the regulatory provisions of the North Carolina Utilities Commission (NCUC), the Public Service Commission of South Carolina (PSCSC), the U.S. Nuclear Regulatory Commission (NRC) and the Federal Energy Regulatory Commission (FERC). Substantially all of Duke Energy Carolinas' operations are regulated and qualify for regulatory accounting treatment. As discussed further in Note 3, Duke Energy Carolinas' operations include one reportable business segment, Franchised Electric. Progress Energy, a wholly owned subsidiary of Duke Energy, is a holding company headquartered in Raleigh, North Carolina, subject to regulation by the FERC. Progress Energy conducts operations through its wholly owned subsidiaries, Progress Energy Carolinas and Progress Energy Florida. As discussed further in Note 3, Progress Energy's operations include one reportable segment, Franchised Electric. Progress Energy Carolinas, an indirect wholly owned subsidiary of Duke Energy, is a regulated public utility primarily engaged in the generation, transmission, distribution and sale of electricity in portions of North Carolina and South Carolina. Progress Energy Carolinas is subject to the regulatory provisions of the NCUC, the PSCSC, the NRC and the FERC. Substantially all of Progress Energy Carolinas' operations are regulated and qualify for regulatory accounting treatment. As discussed further in Note 3, Progress Energy Carolinas' operations include one reportable segment, Franchised Electric. Progress Energy Florida, an indirect wholly owned subsidiary of Duke Energy, is a regulated public utility primarily engaged in the generation, transmission, distribution and sale of electricity in west central Florida. Progress Energy Florida is subject to the regulatory jurisdiction of the Florida Public Service Commission (FPSC), the NRC and the FERC. Substantially all of Progress Energy Florida's operations are regulated and qualify for regulatory accounting treatment. As discussed further in Note 3, Progress Energy Florida's operations include one reportable segment, Franchised Electric. Duke Energy Ohio, an indirect wholly owned subsidiary of Duke Energy, is a combination electric and gas public utility that provides service in the southwestern portion of Ohio and in northern Kentucky through its wholly owned subsidiary, Duke Energy Kentucky, as well as electric generation in parts of Ohio, Illinois and Pennsylvania. Duke Energy Ohio's principal lines of business include generation, transmission and distribution of electricity, the sale of and/or transportation of natural gas, and energy marketing. Duke Energy Ohio conducts competitive auctions for retail electricity supply in Ohio whereby the energy price is recovered from retail customers. Duke Energy Kentucky's principal lines of business include generation, transmission and distribution of electricity, as well as the sale of and/or transportation of natural gas. References herein to Duke Energy Ohio include Duke Energy Ohio and its subsidiaries, unless otherwise noted. Duke Energy Ohio is subject to the regulatory provisions of the Public Utilities Commission of Ohio (PUCO), the Kentucky Public Service Commission (KPSC) and the FERC. Duke Energy Ohio applies regulatory accounting treatment to substantially all of the operations in its Franchised Electric and Gas operating segment. Through November 2011, Duke Energy Ohio applied regulatory accounting treatment to certain rate riders associated with retail generation of its Commercial Power operating segment. See Note 3 for further information about Duke Energy Ohio's business segments. Duke Energy Indiana, an indirect wholly owned subsidiary of Duke Energy, is an electric utility that provides service in north central, central, and southern Indiana. Its primary line of business is generation, transmission and distribution of electricity. Duke Energy Indiana is subject to the regulatory provisions of the Indiana Utility Regulatory Commission (IURC) and the FERC. Substantially all of Duke Energy Indiana's operations are regulated and qualify for regulatory accounting treatment. As discussed further in Note 3, Duke Energy Indiana's operations include one reportable business segment, Franchised Electric. Certain prior year amounts have been reclassified to conform to current year presentation. In addition, prior year financial statements and footnote disclosures for the Progress Energy Registrants have been reclassified to conform to Duke Energy's presentation.
Use Of Estimates	Use of Estimates. To conform to generally accepted accounting principles (GAAP) in the U.S., management makes estimates and assumptions that affect the amounts reported in the Consolidated Financial Statements and Notes. Although these estimates are based on management's best available information at the time, actual results could differ.
Cost-Based Regulation	Cost-Based Regulation. The Duke Energy Registrants account for their regulated operations in accordance with applicable regulatory accounting guidance. The economic effects of regulation can result in a regulated company recording assets for costs that have been or are expected to be approved for recovery from customers in a future period or recording liabilities for amounts that are expected to be returned to customers in the rate-setting process in a period different from the period in which the amounts would be recorded by an unregulated enterprise. Accordingly, the Duke Energy Registrants record assets and liabilities that result from the regulated ratemaking process that would not be recorded under GAAP for nonregulated entities. Regulatory assets and liabilities are amortized consistent with the treatment of the related cost in the ratemaking process. Management continually assesses whether regulatory assets are probable of future recovery by considering factors such as applicable regulatory changes, recent rate orders applicable to other regulated entities and the status of any pending or potential deregulation legislation. Additionally, management continually assesses whether any regulatory liabilities have been incurred. Based on this continual assessment, management believes the existing regulatory assets are probable of recovery and that no regulatory liabilities, other than those recorded, have been incurred. These regulatory assets and liabilities are classified in the Consolidated Balance Sheets as Regulatory assets and Other in Current Assets and as Regulatory liabilities and Other in Current Liabilities, respectively. The Duke Energy Registrants periodically evaluate the applicability of regulatory accounting treatment by considering factors such as regulatory changes and the impact of competition. If cost-based regulation ends or competition increases, the Duke Energy Registrants may have to reduce their asset balances to reflect a market basis less than cost and write-off the associated regulatory assets and liabilities. If it becomes probable that part of the cost of a plant under construction or a recently completed plant will be disallowed for ratemaking purposes and a reasonable estimate of the amount of the disallowance can be made, that amount is recognized as a loss. In November 2011, in conjunction with the PUCO's approval of its new Electric Security Plan (ESP), Duke Energy Ohio ceased applying regulatory accounting treatment to generation operations within its Commercial Power segment. For further information, see Note 4.
Energy Purchases, Fuel Costs And Fuel Cost Deferrals	Energy Purchases, Fuel Costs and Fuel Cost Deferrals. The Duke Energy Registrants utilize cost-tracking mechanisms, commonly referred to as a fuel adjustment clause, to recover the retail portion of fuel and purchased power. The Duke Energy Registrants defer the related cost through Fuel used in electric generation and purchased power — regulated on the Consolidated Statement of Operations, unless a regulatory requirement exists for deferral through Operating Revenues. Fuel used in electric generation and purchased power — regulated includes fuel, purchased power and recoverable costs that are deferred through fuel clauses established by the Subsidiary Registrants' regulators. These clauses allow the Subsidiary Registrants to recover fuel costs, fuel-related costs and portions of purchased power costs through surcharges on customer rates. The Subsidiary Registrants record any under-recovery or over-recovery resulting from the differences between estimated and actual costs as a regulatory asset or regulatory liability until billed or refunded to customers, at which point the differences are adjusted through revenues. Indiana law limits the amount of fuel costs that Duke Energy Indiana can recover to an amount that will not result in earning a return in excess of that allowed by the IURC. As discussed in Note 4, beginning January 1, 2012, Duke Energy Ohio procures energy for its retail customers through a third-party auction. Purchases of energy through the auction process are a pass-through of costs for Duke Energy Ohio, with no affect on earnings. Subsequent to December 31, 2011, Duke Energy Ohio's generation assets are no longer dedicated to retail customers and, accordingly, Duke Energy Ohio can no longer recover their generation assets' energy purchases and fuel costs from regulated customers.
Cash and Cash Equivalents	Cash and Cash Equivalents. All highly liquid investments with maturities of three months or less at the date of acquisition are considered cash equivalents. At December 31, 2012, Duke Energy had cash and cash equivalents of $1,424 million, of which $731 million is held in foreign jurisdictions and is forecasted to be used to fund international operations and investments
Restricted Cash	Restricted Cash. The Duke Energy Registrants have restricted cash related primarily to collateral assets, escrow deposits, and restricted cash of VIEs. Restricted cash balances are reflected in Other within Current Assets and in Other within Investments and Other Assets on the Consolidated Balance Sheets.
Inventory	Inventory. Inventory is comprised of amounts presented in the tables below and is recorded primarily using the average cost method. Inventory related to the Duke Energy Registrants' regulated operations is valued at historical cost consistent with ratemaking treatment. Materials and supplies are recorded as inventory when purchased and subsequently charged to expense or capitalized to property, plant and equipment when installed. Reserves are established for excess and obsolete inventory. Inventory related to the Duke Energy Registrants' nonregulated operations is valued at the lower of cost or market. The following tables present the Duke Energy Registrants' inventory.
Investments In Debt And Equity Securities	Investments in Debt and Equity Securities. The Duke Energy Registrants classify investments into two categories — trading and available-for-sale. Trading securities are reported at fair value in the Consolidated Balance Sheets with net realized and unrealized gains and losses included in earnings each period. Available-for-sale securities are also reported at fair value on the Consolidated Balance Sheets with unrealized gains and losses included in Accumulated Other Comprehensive Income (AOCI) or as a regulatory asset or liability, unless it is determined that the carrying value of an investment is other-than-temporarily impaired. Other-than-temporary impairments related to equity securities and the credit loss portion of debt securities are included in earnings, unless deferred in accordance with regulatory accounting treatment. Investments in debt and equity securities are classified as either short-term investments or long-term investments based on management's intent and ability to sell these securities, taking into consideration illiquidity factors in the current markets with respect to certain investments that have historically provided for a high degree of liquidity, such as investments in auction rate debt securities. See Note 17 for further information on the investments in debt and equity securities, including investments held in the nuclear decommissioning trust funds (NDTF).
Long-Lived Asset Impairments	Long-Lived Asset Impairments. The Duke Energy Registrants evaluate whether long-lived assets, excluding goodwill, have been impaired when circumstances indicate the carrying value of those assets may not be recoverable. For such long-lived assets, an impairment exists when its carrying value exceeds the sum of estimates of the undiscounted cash flows expected to result from the use and eventual disposition of the asset. When alternative courses of action to recover the carrying amount of a long-lived asset are under consideration, a probability-weighted approach is used for developing estimates of future undiscounted cash flows. If the carrying value of the long-lived asset is not recoverable based on these estimated future undiscounted cash flows, the impairment loss is measured as the excess of the carrying value of the asset over its fair value, such that the asset's carrying value is adjusted to its estimated fair value. Management assesses the fair value of long-lived assets using commonly accepted techniques, and may use more than one source. Sources to determine fair value include, but are not limited to, recent third party comparable sales, internally developed discounted cash flow analysis and analysis from outside advisors. Significant changes in market conditions resulting from events such as, among others, changes in commodity prices or the condition of an asset, or a change in management's intent to utilize the asset are generally viewed by management as triggering events to re-assess the cash flows related to the long-lived assets. See Note 12 for further information.
Property, Plant and Equipment	Property, Plant and Equipment. Property, plant and equipment are stated at the lower of historical cost less accumulated depreciation or fair value, if impaired. The Duke Energy Registrants capitalize all construction-related direct labor and material costs, as well as indirect construction costs. Indirect costs include general engineering, taxes and the allowance for funds used during construction (AFUDC). See “AFUDC and Interest Capitalized,” below for additional information. The cost of renewals and betterments that extend the useful life of property, plant and equipment are also capitalized. The cost of repairs, replacements and major maintenance projects, which do not extend the useful life or increase the expected output of the asset, are expensed as incurred. Depreciation is generally computed over the estimated useful life of the asset using the composite straight-line method. For regulated operations, depreciation studies are conducted periodically to update the composite rates and are approved by the various state commissions. The composite weighted-average depreciation rates, excluding nuclear fuel, for each of the Duke Energy Registrants are included in the following table: When the Duke Energy Registrants retire regulated property, plant and equipment under what is considered a normal retirement, the original cost plus the cost of retirement, less salvage value, is charged to accumulated depreciation, consistent with regulated rate-making practices. When it becomes probable that a regulated generation asset will be retired substantially in advance of its original expected useful life or is abandoned, the cost of the asset and the corresponding accumulated depreciation is removed from Cost and Accumulated depreciation and amortization within Property, Plant and Equipment on the Consolidated Balance Sheets and a separate asset is recognized. If the plant is still in operation, the amount is classified as Generation facilities to be retired, net on the Consolidated Balance Sheets. If the plant is no longer operating, then a regulatory asset is recognized. The carrying value of the asset is based on historical cost if the Duke Energy Registrants are allowed to recover the remaining net book value and a full return on the asset. If the Duke Energy Registrants do not expect to recover the full remaining cost and a full return, the carrying value of the asset is based on the lower of cost or the present value of the future revenues expected to be provided to recover the allowable costs discounted at the Duke Energy Registrants' incremental borrowing rate. An impairment is recognized if the net book value of the asset exceeds the present value of the future revenues to be recovered in rates. When the Duke Energy Registrants sell entire regulated operating units, or retire or sell nonregulated properties, the original cost is removed from property and the related accumulated depreciation and amortization balances are reduced. Any gain or loss is recorded in earnings, unless otherwise required by the applicable regulatory body. See Note 10 for further information on the components and estimated useful lives of Duke Energy's property, plant and equipment.
AFUDC And Interest Capitalized	AFUDC and Interest Capitalized. In accordance with applicable regulatory accounting guidance, the Duke Energy Registrants record AFUDC, which represents the estimated debt and equity costs of capital funds necessary to finance the construction of new regulated facilities. The equity component of AFUDC is a non-cash amount within the Consolidated Statements of Operations. AFUDC is capitalized as a component of the cost of property, plant and equipment, with an offsetting credit to Other income and expenses, net on the Consolidated Statements of Operations for the equity component and as an offset to Interest Expense on the Consolidated Statements of Operations for the debt component. After construction is completed, the Duke Energy Registrants are permitted to recover these costs through inclusion in the rate base and the corresponding depreciation expense or nuclear fuel expense. AFUDC equity is a permanent difference item for income tax purposes, thus reducing the Duke Energy Registrants' effective tax rate during the construction phase in which AFUDC equity is being recorded. The effective tax rate is subsequently increased in future periods when the completed property, plant and equipment are placed in service and depreciation of the AFUDC equity commences. See Note 24 for information related to the impacts of AFUDC equity on the Duke Energy Registrants' effective tax rate. For nonregulated operations, interest is capitalized during the construction phase in accordance with the applicable accounting guidance.
Asset Retirement Obligations	Asset Retirement Obligations. The Duke Energy Registrants recognize asset retirement obligations for legal obligations associated with the retirement of long-lived assets that result from the acquisition, construction, development and/or normal use of the asset, and for conditional asset retirement obligations. The term conditional asset retirement obligation refers to a legal obligation to perform an asset retirement activity in which the timing and (or) method of settlement are conditional on a future event that may or may not be within the control of the entity. The obligation to perform the asset retirement activity is unconditional even though uncertainty exists about the timing and (or) method of settlement. Thus, the timing and (or) method of settlement may be conditional on a future event. When recording an asset retirement obligation, the present value of the projected liability is recognized in the period in which it is incurred, if a reasonable estimate of fair value can be made. The liability is then accreted over time by applying an interest method of allocation to the liability. Substantially all accretion is related to regulated operations and is deferred pursuant to regulatory accounting. The present value of the liability is added to the carrying amount of the associated asset and this additional carrying amount is depreciated over the remaining life of the asset. The present value of the initial obligation and subsequent updates are based on discounted cash flows, which include estimates regarding the timing of future cash flows, the selection of discount rates and cost escalation rates, among other factors. These underlying assumptions and estimates are made as of a point in time and are subject to change. The obligations for nuclear decommissioning are based on site-specific cost studies. Duke Energy Carolinas and Progress Energy Carolinas assume prompt dismantlement of the nuclear facilities, which reflects dismantling the site after operations are ceased. Progress Energy Florida assumes the nuclear facility will be placed into a safe storage configuration until the eventual dismantling of the site begins in approximately 40-60 years. The nuclear decommissioning asset retirement obligation also assumes Duke Energy Carolinas, Progress Energy Carolinas and Progress Energy Florida will store spent fuel on site until such time that it can be transferred to a U.S. Department of Energy (DOE) facility. See Note 9 for further information.
Unbilled Revenue	Revenue Recognition and Unbilled Revenue. Revenues on sales of electricity and gas are recognized when either the service is provided or the product is delivered. Unbilled retail revenues are estimated by applying average revenue per kilowatt-hour (kWh) or per thousand cubic feet (Mcf) for all customer classes to the number of estimated kWh or Mcf delivered but not billed. Unbilled wholesale energy revenues are calculated by applying the contractual rate per megawatt-hour (MWh) to the number of estimated MWh delivered but not yet billed. Unbilled wholesale demand revenues are calculated by applying the contractual rate per megawatt (MW) to the MW volume delivered but not yet billed. The amount of unbilled revenues can vary significantly from period to period as a result of numerous factors, including seasonality, weather, customer usage patterns and customer mix. The Duke Energy Registrants had unbilled revenues within Receivables and within Restricted receivables of variable interest entities on their respective Consolidated Balance Sheets as shown in the table below. Additionally, Duke Energy Ohio and Duke Energy Indiana sell, on a revolving basis, nearly all of their retail and wholesale accounts receivable to Cinergy Receivables Company, LLC (CRC). These transfers meet sales/derecognition criteria and, therefore, Duke Energy Ohio and Duke Energy Indiana account for the transfers of receivables to Cinergy Receivables as sales. Accordingly, the receivables sold are not reflected on the Consolidated Balance Sheets of Duke Energy Ohio and Duke Energy Indiana. See Note 18 for further information. Receivables for unbilled revenues related to retail and wholesale accounts receivable at Duke Energy Ohio and Duke Energy Indiana included in the sales of accounts receivable to CRC were as shown in the table below.
Accounting For Risk Management, Hedging Activities And Financial Instruments	Accounting for Risk Management, Hedging Activities and Financial Instruments. The Duke Energy Registrants may use a number of different derivative and non-derivative instruments in connection with their commodity price, interest rate and foreign currency risk management activities, including swaps, futures, forwards and options. All derivative instruments except those that qualify for the normal purchase/normal sale (NPNS) exception within the accounting guidance for derivatives are recorded on the Consolidated Balance Sheets at their fair value. The effective portion of the change in the fair value of derivative instruments designated as cash flow hedges is recorded in AOCI. The effective portion of the change in the fair value of a fair value hedge is offset in net income by changes in the hedged item. The Duke Energy Registrants may designate qualifying derivative instruments as either cash flow hedges or fair value hedges, while others either have not been designated as hedges or do not qualify as a hedge (hereinafter referred to as undesignated contracts). For all contracts accounted for as a hedge, the Duke Energy Registrants prepare formal documentation of the hedge in accordance with the accounting guidance for derivatives. In addition, at inception and at least every three months thereafter, the Duke Energy Registrants formally assess whether the hedge contract is highly effective in offsetting changes in cash flows or fair values of hedged items. The Duke Energy Registrants document hedging activity by transaction type and risk management strategy. See Note 15 for further information.
Captive Insurance Reserves	Captive Insurance Reserves. Duke Energy has captive insurance subsidiaries that provide coverage, on an indemnity basis, to the Subsidiary Registrants as well as certain third parties, on a limited basis, for various business risks and losses, such as property, business interruption, workers' compensation and general liability. Liabilities include provisions for estimated losses incurred but not yet reported (IBNR), as well as provisions for known claims which have been estimated on a claims-incurred basis. IBNR reserve estimates involve the use of assumptions and are primarily based upon historical loss experience, industry data and other actuarial assumptions. Reserve estimates are adjusted in future periods as actual losses differ from historical experience. Duke Energy, through its captive insurance entities, also has reinsurance coverage with third parties, which provides reimbursement for certain losses above a per occurrence and/or aggregate retention. Duke Energy recognizes a reinsurance receivable for recovery of incurred losses under its captive's reinsurance coverage once realization of the receivable is deemed probable.
Unamortized Debt Premium, Discount And Expense	Unamortized Debt Premium, Discount and Expense. Premiums, discounts and expenses incurred with the issuance of outstanding long-term debt are amortized over the terms of the debt issues. Any call premiums or unamortized expenses associated with refinancing higher-cost debt obligations used to finance regulated assets and operations are amortized consistent with regulatory treatment of those items, where appropriate. The amortization expense is recorded as a component of Interest Expense in the Consolidated Statements of Operations and is reflected as Depreciation, amortization and accretion within Net cash provided by operating activities on the Consolidated Statements of Cash Flows.
Loss Contingencies And Environmental Liabilities	Loss Contingencies and Environmental Liabilities. The Duke Energy Registrants are involved in certain legal and environmental matters that arise in the normal course of business. Contingent losses are recorded when it is determined that it is probable that a loss has occurred and the amount of the loss can be reasonably estimated. When a range of the probable loss exists and no amount within the range is a better estimate than any other amount, the Duke Energy Registrants record a loss contingency at the minimum amount in the range. Unless otherwise required by GAAP, legal fees are expensed as incurred. Environmental liabilities are recorded on an undiscounted basis when the necessity for environmental remediation becomes probable and the costs can be reasonably estimated, or when other potential environmental liabilities are reasonably estimable and probable. The Duke Energy Registrants expense environmental expenditures related to conditions caused by past operations that do not generate current or future revenues. Certain environmental expenses receive regulatory accounting treatment, under which the expenses are recorded as regulatory assets. Environmental expenditures related to operations that generate current or future revenues are expensed or capitalized, as appropriate. See Note 5 for further information.
Pension And Other Post-Retirement Benefit Plans	Pension and Other Post-Retirement Benefit Plans. Duke Energy maintains qualified, non-qualified and other post-retirement benefit plans. Eligible employees of the Subsidiary Registrants participate in the respective Duke Energy or Progress Energy qualified, non-qualified and other post-retirement benefit plans and are allocated their proportionate share of benefit costs. See Note 23 for information related to Duke Energy's benefit plans, including certain accounting policies associated with these plans.
Guarantees	Guarantees. Upon issuance or modification of a guarantee, the Duke Energy Registrants recognize a liability at the time of issuance or material modification for the estimated fair value of the obligation it assumes under that guarantee, if any. Fair value is estimated using a probability-weighted approach. The Duke Energy Registrants reduce the obligation over the term of the guarantee or related contract in a systematic and rational method as risk is reduced under the obligation. Any additional contingent loss for guarantee contracts subsequent to the initial recognition of a liability in accordance with applicable accounting guidance is accounted for and recognized at the time a loss is probable and the amount of the loss can be reasonably estimated. The Duke Energy Registrants have entered into various indemnification agreements related to purchase and sale agreements and other types of contractual agreements with vendors and other third parties. These agreements typically cover environmental, tax, litigation and other matters, as well as breaches of representations, warranties and covenants. Typically, claims may be made by third parties for various periods of time, depending on the nature of the claim. Potential exposure under these indemnification agreements can range from a specified to an unlimited dollar amount, depending on the nature of the claim and the particular transaction. See Note 7 for further information.
Stock-based Compensation	Stock-Based Compensation. Stock-based compensation represents the cost related to stock-based awards granted to employees. Duke Energy recognizes stock-based compensation based upon the estimated fair value of the awards, net of estimated forfeitures. The recognition period for these costs begin at either the applicable service inception date or grant date and continues throughout the requisite service period, or for certain share-based awards until the employee becomes retirement eligible, if earlier. Share-based awards, including stock options, but not performance shares, granted to employees that are already retirement eligible are deemed to have vested immediately upon issuance, and, therefore, compensation cost for those awards is recognized on the date such awards are granted. See Note 22 for further information.
Accounting For Purchases And Sales Of Emission Allowances	Accounting For Purchases and Sales of Emission Allowances. Emission allowances are issued by the Environmental Protection Agency (EPA) at zero cost and permit the holder of the allowance to emit certain gaseous by-products of fossil fuel combustion, including sulfur dioxide (SO2) and nitrogen oxide (NOx). Allowances may also be bought and sold via third-party transactions. Allowances allocated to or acquired by the Duke Energy Registrants are held primarily for consumption. Emission allowances at cost are included in Intangibles, net on the Consolidated Balance Sheets and the Duke Energy Registrants recognize expense as the allowances are consumed or sold. Gains or losses on sales of emission allowances by regulated businesses that do not provide for direct recovery through a cost-tracking mechanism and by nonregulated businesses are presented in Gains on Sales of Other Assets and Other, net, in the Consolidated Statements of Operations. For regulated businesses that provide for direct recovery of emission allowances, any gain or loss on sales of recoverable emission allowances are included in the rate structure of the regulated entity and are deferred as a regulatory asset or liability. Future rates charged to retail customers are impacted by any gain or loss on sales of recoverable emission allowances. Purchases and sales of emission allowances are presented gross as investing activities on the Consolidated Statements of Cash Flows. See Note 12 for discussion regarding the impairment of the carrying value of certain emission allowances in 2011.
Income Taxes	Income Taxes. Duke Energy and its subsidiaries file a consolidated federal income tax return and other state and foreign jurisdictional returns as required. Deferred income taxes have been provided for temporary differences between the GAAP and tax carrying amounts of assets and liabilities. These differences create taxable or tax-deductible amounts for future periods. Investment tax credits (ITC) associated with regulated operations are deferred and are amortized as a reduction of income tax expense over the estimated useful lives of the related properties. The Subsidiary Registrants entered into a tax sharing agreement with Duke Energy, where the separate return method is used to allocate tax expenses and benefits to the subsidiaries whose investments or results of operations provide these tax expenses or benefits. The accounting for income taxes essentially represents the income taxes that the Subsidiary Registrants would incur if the Subsidiary Registrants were a separate company filing its own federal tax return as a C-Corporation. The Duke Energy Registrants record unrecognized tax benefits for positions taken or expected to be taken on tax returns, including the decision to exclude certain income or transactions from a return, when a more-likely-than-not threshold is met for a tax position and management believes that the position will be sustained upon examination by the taxing authorities. Management evaluates each position based solely on the technical merits and facts and circumstances of the position, assuming the position will be examined by a taxing authority having full knowledge of all relevant information. The Duke Energy Registrants record the largest amount of the unrecognized tax benefit that is greater than 50% likely of being realized upon settlement or effective settlement. Management considers a tax position effectively settled for the purpose of recognizing previously unrecognized tax benefits when the following conditions exist: (i) the taxing authority has completed its examination procedures, including all appeals and administrative reviews that the taxing authority is required and expected to perform for the tax positions, (ii) the Duke Energy Registrants do not intend to appeal or litigate any aspect of the tax position included in the completed examination, and (iii) it is remote that the taxing authority would examine or reexamine any aspect of the tax position. Deferred taxes are not provided on translation gains and losses where Duke Energy expects earnings of a foreign operation to be indefinitely reinvested. The Duke Energy Registrants record tax-related interest expense in Interest Expense and interest income and penalties in Other Income and Expenses, net, in the Consolidated Statements of Operations. See Note 24 for further information.
Excise Taxes	Excise Taxes. Certain excise taxes levied by state or local governments are collected by the Duke Energy Registrants from their customers. These taxes, which are required to be paid regardless of the Duke Energy Registrants' ability to collect from the customer, are accounted for on a gross basis. When the Duke Energy Registrants act as an agent, and the tax is not required to be remitted if it is not collected from the customer, the taxes are accounted for on a net basis. The Duke Energy Registrants' excise taxes accounted for on a gross basis and recorded as operating revenues in the Consolidated Statements of Operations were as follows:
Foreign Currency Transaction	Foreign Currency Translation. The local currencies of Duke Energy's foreign operations have been determined to be their functional currencies, except for certain foreign operations whose functional currency has been determined to be the U.S. Dollar, based on an assessment of the economic circumstances of the foreign operation. Assets and liabilities of foreign operations, except for those whose functional currency is the U.S. Dollar, are translated into U.S. Dollars at the exchange rates in effect at period end. Translation adjustments resulting from fluctuations in exchange rates are included as a separate component of AOCI. Revenue and expense accounts of these operations are translated at average exchange rates prevailing during the year. Gains and losses arising from balances and transactions denominated in currencies other than the functional currency are included in the results of operations in the period in which they occur.
Dividend Restrictions And Unappropriated Retained Earnings	Dividend Restrictions and Unappropriated Retained Earnings. Duke Energy does not have any legal, regulatory or other restrictions on paying common stock dividends to shareholders. However, as further described in Note 4, due to conditions established by regulators at the time of the Duke Energy/Cinergy merger in April 2006 and the Duke Energy/Progress Energy merger in 2012, certain wholly owned subsidiaries, including Duke Energy Carolinas, Progress Energy Carolinas, Duke Energy Ohio and Duke Energy Indiana, have restrictions on paying dividends or otherwise advancing funds to Duke Energy. At December 31, 2012 and 2011, an insignificant amount of Duke Energy's consolidated Retained earnings balance represents undistributed earnings of equity method investments.
New Accounting Standards [Policy Text Block]	New Accounting Standards. The following new accounting standards were adopted by the Duke Energy Registrants during the year ended December 31, 2012, and the impact of such adoption, if applicable, has been presented in the accompanying Consolidated Financial Statements: Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC) 220 — Comprehensive Income. In June 2011, the FASB amended the existing requirements for presenting comprehensive income in financial statements primarily to increase the prominence of items reported in other comprehensive income (OCI) and to facilitate the convergence of U.S. GAAP and International Financial Reporting Standards (IFRS). Specifically, the revised guidance eliminates the option previously provided to present components of OCI as part of the statement of changes in stockholders' equity. Accordingly, all non-owner changes in stockholders' equity are required to be presented either in a single continuous statement of comprehensive income or in two separate but consecutive financial statements. For the Duke Energy Registrants, this revised guidance was effective on a retrospective basis for interim and annual periods beginning January 1, 2012. The adoption of this standard changed the presentation of the Duke Energy Registrants' financial statements but did not affect the calculation of net income, comprehensive income or earnings per share. ASC 820 — Fair Value Measurements and Disclosures. In May 2011, the FASB amended existing requirements for measuring fair value and for disclosing information about fair value measurements. This revised guidance results in a consistent definition of fair value, as well as common requirements for measurement and disclosure of fair value information between U.S. GAAP and IFRS. In addition, the amendments set forth enhanced disclosure requirements with respect to recurring Level 3 measurements, nonfinancial assets measured or disclosed at fair value, transfers between levels in the fair value hierarchy, and assets and liabilities disclosed but not recorded at fair value. For the Duke Energy Registrants, the revised fair value measurement guidance was effective on a prospective basis for interim and annual periods beginning January 1, 2012. The adoption of this new guidance did not have a significant impact on the Duke Energy Registrants disclosures or their consolidated results of operations, cash flows, or financial position. The following new accounting standards were adopted by Duke Energy during the year ended December 31, 2011, and the impact of such adoption, if applicable has been presented in the accompanying Consolidated Financial Statements: ASC 605 — Revenue Recognition. In October 2009, the FASB issued new revenue recognition accounting guidance in response to practice concerns related to the accounting for revenue arrangements with multiple deliverables. This new accounting guidance primarily applies to all contractual arrangements in which a vendor will perform multiple revenue generating activities and addresses the unit of accounting for arrangements involving multiple deliverables, as well as how arrangement consideration should be allocated to the separate units of accounting. For the Duke Energy Registrants, the new accounting guidance was effective January 1, 2011, and applied on a prospective basis. This new accounting guidance did not have a material impact to the consolidated results of operations, cash flows or financial position of the Duke Energy Registrants. ASC 805 — Business Combinations. In November 2010, the FASB issued new accounting guidance in response to diversity in the interpretation of pro forma information disclosure requirements for business combinations. The new accounting guidance requires an entity to present pro forma financial information as if a business combination occurred at the beginning of the earliest period presented as well as additional disclosures describing the nature and amount of material, nonrecurring pro forma adjustments. This new accounting guidance was effective January 1, 2011, and has been applied to all business combinations consummated after that date. ASC 820 — Fair Value Measurements and Disclosures. In January 2010, the FASB amended existing fair value measurements and disclosures accounting guidance to clarify certain existing disclosure requirements and to require a number of additional disclosures, including amounts and reasons for significant transfers between the three levels of the fair value hierarchy, and presentation of certain information in the reconciliation of recurring Level 3 measurements on a gross basis. For the Duke Energy Registrants, certain portions of this revised accounting guidance were effective on January 1, 2010, with additional disclosures effective for periods beginning January 1, 2011. The adoption of this accounting guidance resulted in additional disclosure in the notes to the consolidated financial statements but did not have an impact on the Duke Energy Registrants' consolidated results of operations, cash flows or financial position. ASC 350 — Intangibles–Goodwill and Other. In September 2011, the FASB amended existing goodwill impairment testing accounting guidance to provide an entity testing goodwill for impairment with the option of performing a qualitative assessment prior to calculating the fair value of a reporting unit in step one of a goodwill impairment test. Under this revised guidance, a qualitative assessment would require an evaluation of economic, industry, and company-specific considerations. If an entity determines, on a basis of such qualitative factors, that the fair value of a reporting unit is more likely than not less than the carrying value of a reporting unit, the two-step impairment test, as required under pre-existing applicable accounting guidance, would be required. Otherwise, no further impairment testing would be required. The revised goodwill impairment testing accounting guidance is effective for the Duke Energy Registrants' annual and interim goodwill impairment tests performed for fiscal years beginning January 1, 2012, with early adoption of this revised guidance permitted for annual and interim goodwill impairment tests performed as of a date before September 15, 2011. Since annual goodwill impairment tests are performed by Duke Energy as of August 31, the Duke Energy Registrants early adopted this revised accounting guidance during the third quarter of 2011 and applied that guidance to their annual goodwill impairment tests for 2011. The following new accounting standards were adopted by Duke Energy during the year ended December 31, 2010, and the impact of such adoption, if applicable has been presented in the accompanying Consolidated Financial Statements: ASC 860 — Transfers and Servicing. In June 2009, the FASB issued revised accounting guidance for transfers and servicing of financial assets and extinguishment of liabilities, to require additional information about transfers of financial assets, including securitization transactions, as well as additional information about an enterprise's continuing exposure to the risks related to transferred financial assets. This revised accounting guidance eliminated the concept of a Qualifying Special Purpose Entity (QSPE) and required those entities which were not subject to consolidation under previous accounting rules to now be assessed for consolidation. In addition, this accounting guidance clarified and amended the derecognition criteria for transfers of financial assets (including transfers of portions of financial assets) and required additional disclosures about a transferor's continuing involvement in transferred financial assets. For Duke Energy, this revised accounting guidance was effective prospectively for transfers of financial assets occurring on or after January 1, 2010, and early adoption of this statement was prohibited. Since 2002, Duke Energy Ohio, Duke Energy Indiana, and Duke Energy Kentucky have sold, on a revolving basis, nearly all of their accounts receivable and related collections through CRC, a bankruptcy-remote QSPE. The securitization transaction was structured to meet the criteria for sale accounting treatment, and, accordingly, Duke Energy did not consolidate CRC, and the transfers were accounted for as sales. Effective with adoption of this revised accounting guidance and ASC 810-Consolidation, as discussed below, the accounting treatment and/or financial statement presentation of Duke Energy's accounts receivable securitization programs was impacted as Duke Energy began consolidating CRC effective January 1, 2010. Duke Energy Ohio's and Duke Energy Indiana's sales of accounts receivable and related financial statement presentation were not impacted by the adoption of ASC 860. ASC 810 — Consolidations. In June 2009, the FASB amended existing consolidation accounting guidance to eliminate the exemption from consolidation for QSPEs, and clarified, but did not significantly change, the criteria for determining whether an entity meets the definition of a VIE. This revised accounting guidance also required an enterprise to qualitatively assess the determination of the primary beneficiary of a VIE based on whether that enterprise has both the power to direct the activities that most significantly impact the economic performance of a VIE and the obligation to absorb losses or the right to receive benefits of a VIE that could potentially be significant to a VIE. In addition, this revised accounting guidance modified existing accounting guidance to require an ongoing evaluation of a VIE's primary beneficiary and amended the types of events that trigger a reassessment of whether an entity is a VIE. Furthermore, this accounting guidance required enterprises to provide additional disclosures about their involvement with VIEs and any significant changes in their risk exposure due to that involvement. For the Duke Energy Registrants, this accounting guidance was effective beginning on January 1, 2010, and is applicable to all entities in which Duke Energy is involved, including entities previously subject to existing accounting guidance for VIEs, as well as any QSPEs that existed as of the effective date. Effective with adoption of this revised accounting guidance, the accounting treatment and/or financial statement presentation of Duke Energy's accounts receivable securitization programs were impacted as Duke Energy began consolidating CRC effective January 1, 2010. Duke Energy Ohio's and Duke Energy Indiana's sales of accounts receivable and related financial statement presentation were not impacted by the adoption of ASC 810. This revised accounting guidance did not have a significant impact on any of the Duke Energy Registrants' other interests in VIEs. ASC 820 — Fair Value Measurements and Disclosures. In January 2010, the FASB amended existing fair value measurements and disclosures accounting guidance to clarify certain existing disclosure requirements and to require a number of additional disclosures, including amounts and reasons for significant transfers between the three levels of the fair value hierarchy, and presentation of certain information in the reconciliation of recurring Level 3 measurements on a gross basis. For the Duke Energy Registrants, certain portions of this revised accounting guidance were effective on January 1, 2010, with additional disclosures effective for periods beginning January 1, 2011. The initial adoption of this accounting guidance resulted in additional disclosure in the notes to the consolidated financial statements but did not have an impact on the Duke Energy Registrants' consolidated results of operations, cash flows or financial position. The following new Accounting Standards Updates (ASU) have been issued, but have not yet been adopted by Duke Energy, as of December 31, 2012. ASC 210 — Balance Sheet. In December 2011, the FASB issued revised accounting guidance to amend the existing disclosure requirements for offsetting financial assets and liabilities to enhance current disclosures, as well as to improve comparability of balance sheets prepared under U.S. GAAP and IFRS. The revised disclosure guidance affects all companies that have financial instruments and derivative instruments that are either offset in the balance sheet (i.e., presented on a net basis) or subject to an enforceable master netting arrangement and/or similar agreement. The revised guidance requires that certain enhanced quantitative and qualitative disclosures be made with respect to a company's netting arrangements and/or rights of setoff associated with its financial instruments and/or derivative instruments including associated collateral. For the Duke Energy Registrants, the revised disclosure guidance is effective on a retrospective basis for interim and annual periods beginning January 1, 2013. Other than additional disclosures, this revised guidance does not impact the Duke Energy Registrants' consolidated results of operations, cash flows or financial position. ASC 220 — Comprehensive Income. In February 2013, the FASB amended the existing requirements for presenting comprehensive income in financial statements to improve the reporting of reclassifications out of AOCI. The amendments in this Update seek to attain that objective by requiring an entity to report the effect of significant reclassifications out of AOCI on the respective line items in net income if the amount being reclassified is required under U.S. GAAP to be reclassified in its entirety to net income. For other amounts that are not required under U.S. GAAP to be reclassified in their entirety to net income in the same reporting period, an entity is required to cross-reference other disclosures required under U.S. GAAP that provide additional detail about those amounts. This would be the case when a portion of the amount reclassified out of AOCI is reclassified to a balance sheet account (for example, inventory) instead of directly to income or expense in the same reporting period. For the Duke Energy Registrants, this revised guidance is effective on a prospective basis for interim and annual periods beginning January 1, 2013. Other than additional disclosures or a change in the presentation on the statement of comprehensive income, this revised guidance does not impact the Duke Energy Registrants' consolidated results of operations, cash flows or financial position.

Reverse Stock Split.

On July 2, 2012, just prior to the close of the merger with Progress Energy, Duke Energy executed a one-for-three reverse stock split with respect to the issued and outstanding shares of Duke Energy common stock. All per-share amounts included in this Form 10-K are presented as if the one-for-three reverse stock split had been effective from the beginning of the earliest period presented.

Cost-Based Regulation

Cost-Based Regulation.

The Duke Energy Registrants account for their regulated operations in accordance with applicable regulatory accounting guidance. The economic effects of regulation can result in a regulated company recording assets for costs that have been or are expected to be approved for recovery from customers in a future period or recording liabilities for amounts that are expected to be returned to customers in the rate-setting process in a period different from the period in which the amounts would be recorded by an unregulated enterprise. Accordingly, the Duke Energy Registrants record assets and liabilities that result from the regulated ratemaking process that would not be recorded under GAAP for nonregulated entities. Regulatory assets and liabilities are amortized consistent with the treatment of the related cost in the ratemaking process. Management continually assesses whether regulatory assets are probable of future recovery by considering factors such as applicable regulatory changes, recent rate orders applicable to other regulated entities and the status of any pending or potential deregulation legislation. Additionally, management continually assesses whether any regulatory liabilities have been incurred. Based on this continual assessment, management believes the existing regulatory assets are probable of recovery and that no regulatory liabilities, other than those recorded, have been incurred. These regulatory assets and liabilities are classified in the Consolidated Balance Sheets as Regulatory assets and Other in Current Assets and as Regulatory liabilities and Other in Current Liabilities, respectively. The Duke Energy Registrants periodically evaluate the applicability of regulatory accounting treatment by considering factors such as regulatory changes and the impact of competition. If cost-based regulation ends or competition increases, the Duke Energy Registrants may have to reduce their asset balances to reflect a market basis less than cost and write-off the associated regulatory assets and liabilities. If it becomes probable that part of the cost of a plant under construction or a recently completed plant will be disallowed for ratemaking purposes and a reasonable estimate of the amount of the disallowance can be made, that amount is recognized as a loss.

In November 2011, in conjunction with the PUCO's approval of its new Electric Security Plan (ESP), Duke Energy Ohio ceased applying regulatory accounting treatment to generation operations within its Commercial Power segment.

For further information, see Note 4.

Cash and Cash Equivalents

Cash and Cash Equivalents.

All highly liquid investments with maturities of three months or less at the date of acquisition are considered cash equivalents. At December 31, 2012, Duke Energy had cash and cash equivalents of $1,424 million, of which $731 million is held in foreign jurisdictions and is forecasted to be used to fund international operations and investments.

Inventory

Inventory.

Inventory is comprised of amounts presented in the tables below and is recorded primarily using the average cost method. Inventory related to the Duke Energy Registrants' regulated operations is valued at historical cost consistent with ratemaking treatment. Materials and supplies are recorded as inventory when purchased and subsequently charged to expense or capitalized to property, plant and equipment when installed. Reserves are established for excess and obsolete inventory. Inventory related to the Duke Energy Registrants' nonregulated operations is valued at the lower of cost or market. The following tables present the Duke Energy Registrants' inventory.

Duke Energy Ohio has agreements with a third party through which title of natural gas inventory purchased by Duke Energy Ohio is transferred to a third party. Under the agreements, the gas inventory is stored and managed for Duke Energy Ohio and is delivered on demand. As a result of the agreements, the combined natural gas inventory of approximately $44 million and $50 million being held by a third party as of December 31, 2012, and December 31, 2011, respectively, was classified as Other within Current Assets on the Consolidated Balance Sheets.

Goodwill

Goodwill.

Duke Energy and Duke Energy Ohio perform annual goodwill impairment tests as of August 31 each year and update these tests between annual tests if events or circumstances occur that would more likely than not reduce the fair value of a reporting unit below its carrying value.

In 2012, Progress Energy changed its goodwill impairment testing date from October 31 to August 31. The change in the goodwill impairment test date is preferable as it better aligns the annual goodwill impairment testing procedures with the testing procedures of Duke Energy. The change in accounting principle did not accelerate, delay, avoid, or cause a goodwill impairment charge. Neither the change in the goodwill impairment testing date nor the merger resulted in any changes to the Progress Energy reporting units. Due to significant judgments and estimates that are utilized in a goodwill impairment analysis, Progress Energy determined it was impracticable to objectively determine, without the use of hindsight, projected cash flows and related valuation estimates as of each August 31, for periods prior to August 31, 2012. As such, the change in the annual goodwill impairment testing date was prospectively applied from August 31, 2012.

Duke Energy, Progress Energy and Duke Energy Ohio perform the annual review for goodwill impairment at the reporting unit level, which Duke Energy and Progress Energy have determined to be an operating segment or one level below and which Duke Energy Ohio has determined to be an operating segment.

The annual goodwill impairment test may first consider qualitative factors to determine whether it is more likely than not (i.e. greater than 50 percent chance) that the fair value of a reporting unit is less than its book value. This is sometimes referred to as “step zero” and is an optional step in the annual goodwill impairment analysis (see further discussion as discussed in “New Accounting Standards” below). If the results of qualitative assessments indicate that the fair value of a reporting unit is more likely than not less than the carrying value of the reporting unit, the two-step impairment test is required. Step one of the impairment test involves comparing the fair values of reporting units with their carrying values, including goodwill. If the carrying amount is less than fair value in step one, further testing of goodwill is not performed. If the carrying amount of a reporting unit exceeds the reporting unit's fair value, step two must be performed to determine the amount, if any, of the goodwill impairment loss. Step two of the goodwill impairment test involves comparing the implied fair value of the reporting unit's goodwill against the carrying value of the goodwill. Under step two, determining the implied fair value of goodwill requires the valuation of a reporting unit's identifiable tangible and intangible assets and liabilities as if the reporting unit had been acquired in a business combination on the testing date. The difference between the fair value of the entire reporting unit as determined in step one and the net fair value of all identifiable assets and liabilities represents the implied fair value of goodwill. The goodwill impairment charge, if any, would be the excess of the carrying amount of goodwill over the implied fair value of goodwill upon the completion of step two.

As a result of the Progress Energy merger, Duke Energy, Progress Energy and Duke Energy Ohio performed step one of the goodwill impairment test as of August 31, 2012, and concluded the fair value of the reporting units exceeded their respective carrying values, and thus, did not record any impairment charges. In 2011, Duke Energy and Duke Energy Ohio performed the qualitative assessments under step zero and concluded that it was more likely than not the fair value of each reporting unit exceeded its carrying value. In 2011, Progress Energy performed step one of the goodwill impairment test, which indicated the carrying amounts of goodwill were not impaired. In 2010, Duke Energy, Progress Energy and Duke Energy Ohio used the two-step process to test goodwill for impairment, which resulted in impairments recorded by Duke Energy and Duke Energy Ohio.

See Note 12 for further information.

Property, Plant and Equipment

Property, Plant and Equipment.

Property, plant and equipment are stated at the lower of historical cost less accumulated depreciation or fair value, if impaired. The Duke Energy Registrants capitalize all construction-related direct labor and material costs, as well as indirect construction costs. Indirect costs include general engineering, taxes and the allowance for funds used during construction (AFUDC). See “AFUDC and Interest Capitalized,” below for additional information. The cost of renewals and betterments that extend the useful life of property, plant and equipment are also capitalized. The cost of repairs, replacements and major maintenance projects, which do not extend the useful life or increase the expected output of the asset, are expensed as incurred. Depreciation is generally computed over the estimated useful life of the asset using the composite straight-line method. For regulated operations, depreciation studies are conducted periodically to update the composite rates and are approved by the various state commissions. The composite weighted-average depreciation rates, excluding nuclear fuel, for each of the Duke Energy Registrants are included in the following table:

When the Duke Energy Registrants retire regulated property, plant and equipment under what is considered a normal retirement, the original cost plus the cost of retirement, less salvage value, is charged to accumulated depreciation, consistent with regulated rate-making practices. When it becomes probable that a regulated generation asset will be retired substantially in advance of its original expected useful life or is abandoned, the cost of the asset and the corresponding accumulated depreciation is removed from Cost and Accumulated depreciation and amortization within Property, Plant and Equipment on the Consolidated Balance Sheets and a separate asset is recognized. If the plant is still in operation, the amount is classified as Generation facilities to be retired, net on the Consolidated Balance Sheets. If the plant is no longer operating, then a regulatory asset is recognized. The carrying value of the asset is based on historical cost if the Duke Energy Registrants are allowed to recover the remaining net book value and a full return on the asset. If the Duke Energy Registrants do not expect to recover the full remaining cost and a full return, the carrying value of the asset is based on the lower of cost or the present value of the future revenues expected to be provided to recover the allowable costs discounted at the Duke Energy Registrants' incremental borrowing rate. An impairment is recognized if the net book value of the asset exceeds the present value of the future revenues to be recovered in rates.

When the Duke Energy Registrants sell entire regulated operating units, or retire or sell nonregulated properties, the original cost is removed from property and the related accumulated depreciation and amortization balances are reduced. Any gain or loss is recorded in earnings, unless otherwise required by the applicable regulatory body.

See Note 10 for further information on the components and estimated useful lives of Duke Energy's property, plant and equipment.

AFUDC And Interest Capitalized

AFUDC and Interest Capitalized.

In accordance with applicable regulatory accounting guidance, the Duke Energy Registrants record AFUDC, which represents the estimated debt and equity costs of capital funds necessary to finance the construction of new regulated facilities. The equity component of AFUDC is a non-cash amount within the Consolidated Statements of Operations. AFUDC is capitalized as a component of the cost of property, plant and equipment, with an offsetting credit to Other income and expenses, net on the Consolidated Statements of Operations for the equity component and as an offset to Interest Expense on the Consolidated Statements of Operations for the debt component. After construction is completed, the Duke Energy Registrants are permitted to recover these costs through inclusion in the rate base and the corresponding depreciation expense or nuclear fuel expense.

AFUDC equity is a permanent difference item for income tax purposes, thus reducing the Duke Energy Registrants' effective tax rate during the construction phase in which AFUDC equity is being recorded. The effective tax rate is subsequently increased in future periods when the completed property, plant and equipment are placed in service and depreciation of the AFUDC equity commences. See Note 24 for information related to the impacts of AFUDC equity on the Duke Energy Registrants' effective tax rate.

For nonregulated operations, interest is capitalized during the construction phase in accordance with the applicable accounting guidance.

Unbilled Revenue

Revenue Recognition and Unbilled Revenue.

Revenues on sales of electricity and gas are recognized when either the service is provided or the product is delivered. Unbilled retail revenues are estimated by applying average revenue per kilowatt-hour (kWh) or per thousand cubic feet (Mcf) for all customer classes to the number of estimated kWh or Mcf delivered but not billed. Unbilled wholesale energy revenues are calculated by applying the contractual rate per megawatt-hour (MWh) to the number of estimated MWh delivered but not yet billed. Unbilled wholesale demand revenues are calculated by applying the contractual rate per megawatt (MW) to the MW volume delivered but not yet billed. The amount of unbilled revenues can vary significantly from period to period as a result of numerous factors, including seasonality, weather, customer usage patterns and customer mix.

The Duke Energy Registrants had unbilled revenues within Receivables and within Restricted receivables of variable interest entities on their respective Consolidated Balance Sheets as shown in the table below.

Additionally, Duke Energy Ohio and Duke Energy Indiana sell, on a revolving basis, nearly all of their retail and wholesale accounts receivable to Cinergy Receivables Company, LLC (CRC). These transfers meet sales/derecognition criteria and, therefore, Duke Energy Ohio and Duke Energy Indiana account for the transfers of receivables to Cinergy Receivables as sales. Accordingly, the receivables sold are not reflected on the Consolidated Balance Sheets of Duke Energy Ohio and Duke Energy Indiana. See Note 18 for further information. Receivables for unbilled revenues related to retail and wholesale accounts receivable at Duke Energy Ohio and Duke Energy Indiana included in the sales of accounts receivable to CRC were as shown in the table below.

Captive Insurance Reserves

Captive Insurance Reserves.

Duke Energy has captive insurance subsidiaries that provide coverage, on an indemnity basis, to the Subsidiary Registrants as well as certain third parties, on a limited basis, for various business risks and losses, such as property, business interruption, workers' compensation and general liability. Liabilities include provisions for estimated losses incurred but not yet reported (IBNR), as well as provisions for known claims which have been estimated on a claims-incurred basis. IBNR reserve estimates involve the use of assumptions and are primarily based upon historical loss experience, industry data and other actuarial assumptions. Reserve estimates are adjusted in future periods as actual losses differ from historical experience.

Duke Energy, through its captive insurance entities, also has reinsurance coverage with third parties, which provides reimbursement for certain losses above a per occurrence and/or aggregate retention. Duke Energy recognizes a reinsurance receivable for recovery of incurred losses under its captive's reinsurance coverage once realization of the receivable is deemed probable.

Loss Contingencies And Environmental Liabilities

Loss Contingencies and Environmental Liabilities.

The Duke Energy Registrants are involved in certain legal and environmental matters that arise in the normal course of business. Contingent losses are recorded when it is determined that it is probable that a loss has occurred and the amount of the loss can be reasonably estimated. When a range of the probable loss exists and no amount within the range is a better estimate than any other amount, the Duke Energy Registrants record a loss contingency at the minimum amount in the range. Unless otherwise required by GAAP, legal fees are expensed as incurred.

Environmental liabilities are recorded on an undiscounted basis when the necessity for environmental remediation becomes probable and the costs can be reasonably estimated, or when other potential environmental liabilities are reasonably estimable and probable. The Duke Energy Registrants expense environmental expenditures related to conditions caused by past operations that do not generate current or future revenues. Certain environmental expenses receive regulatory accounting treatment, under which the expenses are recorded as regulatory assets. Environmental expenditures related to operations that generate current or future revenues are expensed or capitalized, as appropriate.

See Note 5 for further information.

Severance And Special Termination Benefits

Severance and Special Termination Benefits.

Duke Energy has an ongoing severance plan under which, in general, the longer a terminated employee worked prior to termination the greater the amount of severance benefits. The Duke Energy Registrants record a liability for involuntary severance once an involuntary severance plan is committed to by management, or sooner, if involuntary severances are probable and the related severance benefits can be reasonably estimated. For involuntary severance benefits that are incremental to its ongoing severance plan benefits, Duke Energy measures the obligation and records the expense at its fair value at the communication date if there are no future service requirements, or, if future service is required to receive the termination benefit, ratably over the service period. From time to time, Duke Energy offers special termination benefits under voluntary severance programs. Special termination benefits are measured upon employee acceptance and recorded immediately absent a significant retention period. If a significant retention period exists, the cost of the special termination benefits are recorded ratably over the remaining service periods of the affected employees. Employee acceptance of voluntary severance benefits is determined by management based on the facts and circumstances of the special termination benefits being offered.

See Note 21 for further information.

Stock-based Compensation

Stock-Based Compensation.

Stock-based compensation represents the cost related to stock-based awards granted to employees. Duke Energy recognizes stock-based compensation based upon the estimated fair value of the awards, net of estimated forfeitures. The recognition period for these costs begin at either the applicable service inception date or grant date and continues throughout the requisite service period, or for certain share-based awards until the employee becomes retirement eligible, if earlier. Share-based awards, including stock options, but not performance shares, granted to employees that are already retirement eligible are deemed to have vested immediately upon issuance, and, therefore, compensation cost for those awards is recognized on the date such awards are granted.

See Note 22 for further information.

Income Taxes

Income Taxes.

Duke Energy and its subsidiaries file a consolidated federal income tax return and other state and foreign jurisdictional returns as required. Deferred income taxes have been provided for temporary differences between the GAAP and tax carrying amounts of assets and liabilities. These differences create taxable or tax-deductible amounts for future periods. Investment tax credits (ITC) associated with regulated operations are deferred and are amortized as a reduction of income tax expense over the estimated useful lives of the related properties.

The Subsidiary Registrants entered into a tax sharing agreement with Duke Energy, where the separate return method is used to allocate tax expenses and benefits to the subsidiaries whose investments or results of operations provide these tax expenses or benefits. The accounting for income taxes essentially represents the income taxes that the Subsidiary Registrants would incur if the Subsidiary Registrants were a separate company filing its own federal tax return as a C-Corporation. The Duke Energy Registrants record unrecognized tax benefits for positions taken or expected to be taken on tax returns, including the decision to exclude certain income or transactions from a return, when a more-likely-than-not threshold is met for a tax position and management believes that the position will be sustained upon examination by the taxing authorities. Management evaluates each position based solely on the technical merits and facts and circumstances of the position, assuming the position will be examined by a taxing authority having full knowledge of all relevant information. The Duke Energy Registrants record the largest amount of the unrecognized tax benefit that is greater than 50% likely of being realized upon settlement or effective settlement. Management considers a tax position effectively settled for the purpose of recognizing previously unrecognized tax benefits when the following conditions exist: (i) the taxing authority has completed its examination procedures, including all appeals and administrative reviews that the taxing authority is required and expected to perform for the tax positions, (ii) the Duke Energy Registrants do not intend to appeal or litigate any aspect of the tax position included in the completed examination, and (iii) it is remote that the taxing authority would examine or reexamine any aspect of the tax position. Deferred taxes are not provided on translation gains and losses where Duke Energy expects earnings of a foreign operation to be indefinitely reinvested.

The Duke Energy Registrants record tax-related interest expense in Interest Expense and interest income and penalties in Other Income and Expenses, net, in the Consolidated Statements of Operations.

See Note 24 for further information.

Excise Taxes

Excise Taxes.

Certain excise taxes levied by state or local governments are collected by the Duke Energy Registrants from their customers. These taxes, which are required to be paid regardless of the Duke Energy Registrants' ability to collect from the customer, are accounted for on a gross basis. When the Duke Energy Registrants act as an agent, and the tax is not required to be remitted if it is not collected from the customer, the taxes are accounted for on a net basis. The Duke Energy Registrants' excise taxes accounted for on a gross basis and recorded as operating revenues in the Consolidated Statements of Operations were as follows:

Dividend Restrictions And Unappropriated Retained Earnings

Dividend Restrictions and Unappropriated Retained Earnings.

Duke Energy does not have any legal, regulatory or other restrictions on paying common stock dividends to shareholders. However, as further described in Note 4, due to conditions established by regulators at the time of the Duke Energy/Cinergy merger in April 2006 and the Duke Energy/Progress Energy merger in 2012, certain wholly owned subsidiaries, including Duke Energy Carolinas, Progress Energy Carolinas, Duke Energy Ohio and Duke Energy Indiana, have restrictions on paying dividends or otherwise advancing funds to Duke Energy. At December 31, 2012 and 2011, an insignificant amount of Duke Energy's consolidated Retained earnings balance represents undistributed earnings of equity method investments.

Organization

Nature of Operations and Basis of Consolidation.

Duke Energy Corporation (collectively with its subsidiaries, Duke Energy), is an energy company headquartered in Charlotte, North Carolina. Duke Energy operates in the United States (U.S.) and Latin America primarily through its direct and indirect subsidiaries. Duke Energy's subsidiaries included Duke Energy Carolinas, LLC (Duke Energy Carolinas), Duke Energy Ohio, Inc. (Duke Energy Ohio), which includes Duke Energy Kentucky, Inc. (Duke Energy Kentucky), and Duke Energy Indiana, Inc. (Duke Energy Indiana) prior to the merger with Progress Energy, Inc. (Progress Energy). On July 2, 2012, Duke Energy merged with Progress Energy, with Duke Energy continuing as the surviving corporation, and Progress Energy becoming a subsidiary of Duke Energy. Carolina Power & Light Company d/b/a Progress Energy Carolinas, Inc. (Progress Energy Carolinas) and Florida Power Corporation d/b/a Progress Energy Florida, Inc. (Progress Energy Florida), Progress Energy's regulated utility subsidiaries, are now indirect subsidiaries of Duke Energy. Duke Energy's consolidated financial statements include Progress Energy, Progress Energy Carolinas and Progress Energy Florida activity beginning July 2, 2012. See Note 2 for additional information regarding the merger. When discussing Duke Energy's consolidated financial information, it necessarily includes the results of its six separate subsidiary registrants, Duke Energy Carolinas, Progress Energy, Progress Energy Carolinas, Progress Energy Florida, Duke Energy Ohio and Duke Energy Indiana (collectively referred to as the Subsidiary Registrants), which, along with Duke Energy, are collectively referred to as the Duke Energy Registrants.

Progress Energy, Progress Energy Carolinas and Progress Energy Florida (collectively referred to as the Progress Energy Registrants) continue to maintain reporting requirements as SEC registrants. In accordance with SEC guidance, the Progress Energy Registrants did not reflect the impacts of acquisition accounting from the merger with Duke Energy, whereby the adjustments of assets and liabilities to fair value and the resultant goodwill would be shown on the financial statements of the Progress Energy Registrants. These adjustments were recorded by Duke Energy.

The information in these combined notes relates to each of the Duke Energy Registrants as noted in the Index to the Combined Notes. However, none of the registrants makes any representation as to information related solely to Duke Energy or the subsidiaries of Duke Energy other than itself. As discussed further in Note 3, Duke Energy operates three reportable business segments: U.S. Franchised Electric and Gas (USFE&G), Commercial Power and International Energy. The remainder of Duke Energy's operations is presented as Other.

These Consolidated Financial Statements include, after eliminating intercompany transactions and balances, the accounts of the Duke Energy Registrants and all majority-owned subsidiaries where the respective Duke Energy Registrants have control and those variable interest entities (VIEs) where the respective Duke Energy Registrants are the primary beneficiary. These Consolidated Financial Statements also reflect the Duke Energy Registrants' proportionate share of certain generation and transmission facilities. In January 2012, Duke Energy Ohio completed the sale of its 75% ownership of the Vermillion Generating Station (Vermillion); upon the close, Duke Energy Indiana purchased a 62.5% interest in the station. See Note 2 for further discussion.

Duke Energy Carolinas, a wholly owned subsidiary of Duke Energy, is an electric utility company that generates, transmits, distributes and sells electricity in North Carolina and South Carolina. Duke Energy Carolinas is subject to the regulatory provisions of the North Carolina Utilities Commission (NCUC), the Public Service Commission of South Carolina (PSCSC), the U.S. Nuclear Regulatory Commission (NRC) and the Federal Energy Regulatory Commission (FERC). Substantially all of Duke Energy Carolinas' operations are regulated and qualify for regulatory accounting treatment. As discussed further in Note 3, Duke Energy Carolinas' operations include one reportable business segment, Franchised Electric.

Progress Energy, a wholly owned subsidiary of Duke Energy, is a holding company headquartered in Raleigh, North Carolina, subject to regulation by the FERC. Progress Energy conducts operations through its wholly owned subsidiaries, Progress Energy Carolinas and Progress Energy Florida. As discussed further in Note 3, Progress Energy's operations include one reportable segment, Franchised Electric.

Progress Energy Carolinas, an indirect wholly owned subsidiary of Duke Energy, is a regulated public utility primarily engaged in the generation, transmission, distribution and sale of electricity in portions of North Carolina and South Carolina. Progress Energy Carolinas is subject to the regulatory provisions of the NCUC, the PSCSC, the NRC and the FERC. Substantially all of Progress Energy Carolinas' operations are regulated and qualify for regulatory accounting treatment. As discussed further in Note 3, Progress Energy Carolinas' operations include one reportable segment, Franchised Electric.

Progress Energy Florida, an indirect wholly owned subsidiary of Duke Energy, is a regulated public utility primarily engaged in the generation, transmission, distribution and sale of electricity in west central Florida. Progress Energy Florida is subject to the regulatory jurisdiction of the Florida Public Service Commission (FPSC), the NRC and the FERC. Substantially all of Progress Energy Florida's operations are regulated and qualify for regulatory accounting treatment. As discussed further in Note 3, Progress Energy Florida's operations include one reportable segment, Franchised Electric.

Duke Energy Ohio, an indirect wholly owned subsidiary of Duke Energy, is a combination electric and gas public utility that provides service in the southwestern portion of Ohio and in northern Kentucky through its wholly owned subsidiary, Duke Energy Kentucky, as well as electric generation in parts of Ohio, Illinois and Pennsylvania. Duke Energy Ohio's principal lines of business include generation, transmission and distribution of electricity, the sale of and/or transportation of natural gas, and energy marketing. Duke Energy Ohio conducts competitive auctions for retail electricity supply in Ohio whereby the energy price is recovered from retail customers. Duke Energy Kentucky's principal lines of business include generation, transmission and distribution of electricity, as well as the sale of and/or transportation of natural gas. References herein to Duke Energy Ohio include Duke Energy Ohio and its subsidiaries, unless otherwise noted. Duke Energy Ohio is subject to the regulatory provisions of the Public Utilities Commission of Ohio (PUCO), the Kentucky Public Service Commission (KPSC) and the FERC. Duke Energy Ohio applies regulatory accounting treatment to substantially all of the operations in its Franchised Electric and Gas operating segment. Through November 2011, Duke Energy Ohio applied regulatory accounting treatment to certain rate riders associated with retail generation of its Commercial Power operating segment. See Note 3 for further information about Duke Energy Ohio's business segments.

Duke Energy Indiana, an indirect wholly owned subsidiary of Duke Energy, is an electric utility that provides service in north central, central, and southern Indiana. Its primary line of business is generation, transmission and distribution of electricity. Duke Energy Indiana is subject to the regulatory provisions of the Indiana Utility Regulatory Commission (IURC) and the FERC. Substantially all of Duke Energy Indiana's operations are regulated and qualify for regulatory accounting treatment. As discussed further in Note 3, Duke Energy Indiana's operations include one reportable business segment, Franchised Electric.

Certain prior year amounts have been reclassified to conform to current year presentation. In addition, prior year financial statements and footnote disclosures for the Progress Energy Registrants have been reclassified to conform to Duke Energy's presentation.

Cost-Based Regulation

Cost-Based Regulation.

The Duke Energy Registrants account for their regulated operations in accordance with applicable regulatory accounting guidance. The economic effects of regulation can result in a regulated company recording assets for costs that have been or are expected to be approved for recovery from customers in a future period or recording liabilities for amounts that are expected to be returned to customers in the rate-setting process in a period different from the period in which the amounts would be recorded by an unregulated enterprise. Accordingly, the Duke Energy Registrants record assets and liabilities that result from the regulated ratemaking process that would not be recorded under GAAP for nonregulated entities. Regulatory assets and liabilities are amortized consistent with the treatment of the related cost in the ratemaking process. Management continually assesses whether regulatory assets are probable of future recovery by considering factors such as applicable regulatory changes, recent rate orders applicable to other regulated entities and the status of any pending or potential deregulation legislation. Additionally, management continually assesses whether any regulatory liabilities have been incurred. Based on this continual assessment, management believes the existing regulatory assets are probable of recovery and that no regulatory liabilities, other than those recorded, have been incurred. These regulatory assets and liabilities are classified in the Consolidated Balance Sheets as Regulatory assets and Other in Current Assets and as Regulatory liabilities and Other in Current Liabilities, respectively. The Duke Energy Registrants periodically evaluate the applicability of regulatory accounting treatment by considering factors such as regulatory changes and the impact of competition. If cost-based regulation ends or competition increases, the Duke Energy Registrants may have to reduce their asset balances to reflect a market basis less than cost and write-off the associated regulatory assets and liabilities. If it becomes probable that part of the cost of a plant under construction or a recently completed plant will be disallowed for ratemaking purposes and a reasonable estimate of the amount of the disallowance can be made, that amount is recognized as a loss.

In November 2011, in conjunction with the PUCO's approval of its new Electric Security Plan (ESP), Duke Energy Ohio ceased applying regulatory accounting treatment to generation operations within its Commercial Power segment.

For further information, see Note 4.

Cash and Cash Equivalents

Cash and Cash Equivalents.

All highly liquid investments with maturities of three months or less at the date of acquisition are considered cash equivalents. At December 31, 2012, Duke Energy had cash and cash equivalents of $1,424 million, of which $731 million is held in foreign jurisdictions and is forecasted to be used to fund international operations and investments.

Inventory

Inventory.

Inventory is comprised of amounts presented in the tables below and is recorded primarily using the average cost method. Inventory related to the Duke Energy Registrants' regulated operations is valued at historical cost consistent with ratemaking treatment. Materials and supplies are recorded as inventory when purchased and subsequently charged to expense or capitalized to property, plant and equipment when installed. Reserves are established for excess and obsolete inventory. Inventory related to the Duke Energy Registrants' nonregulated operations is valued at the lower of cost or market. The following tables present the Duke Energy Registrants' inventory.

Long-Lived Asset Impairments

Long-Lived Asset Impairments.

The Duke Energy Registrants evaluate whether long-lived assets, excluding goodwill, have been impaired when circumstances indicate the carrying value of those assets may not be recoverable. For such long-lived assets, an impairment exists when its carrying value exceeds the sum of estimates of the undiscounted cash flows expected to result from the use and eventual disposition of the asset. When alternative courses of action to recover the carrying amount of a long-lived asset are under consideration, a probability-weighted approach is used for developing estimates of future undiscounted cash flows. If the carrying value of the long-lived asset is not recoverable based on these estimated future undiscounted cash flows, the impairment loss is measured as the excess of the carrying value of the asset over its fair value, such that the asset's carrying value is adjusted to its estimated fair value.

Management assesses the fair value of long-lived assets using commonly accepted techniques, and may use more than one source. Sources to determine fair value include, but are not limited to, recent third party comparable sales, internally developed discounted cash flow analysis and analysis from outside advisors. Significant changes in market conditions resulting from events such as, among others, changes in commodity prices or the condition of an asset, or a change in management's intent to utilize the asset are generally viewed by management as triggering events to re-assess the cash flows related to the long-lived assets.

See Note 12 for further information.

Nuclear Fuel

Nuclear Fuel.

Nuclear fuel is classified as Property, Plant and Equipment in the Consolidated Balance Sheets. Nuclear fuel in the front-end fuel processing phase is considered work in progress and not amortized until placed in service. Amortization of nuclear fuel is included within Fuel used in electric generation and purchased power-regulated in the Consolidated Statements of Operations. The amortization is recorded using the units-of-production method.

Asset Retirement Obligations

Asset Retirement Obligations.

The Duke Energy Registrants recognize asset retirement obligations for legal obligations associated with the retirement of long-lived assets that result from the acquisition, construction, development and/or normal use of the asset, and for conditional asset retirement obligations. The term conditional asset retirement obligation refers to a legal obligation to perform an asset retirement activity in which the timing and (or) method of settlement are conditional on a future event that may or may not be within the control of the entity. The obligation to perform the asset retirement activity is unconditional even though uncertainty exists about the timing and (or) method of settlement. Thus, the timing and (or) method of settlement may be conditional on a future event. When recording an asset retirement obligation, the present value of the projected liability is recognized in the period in which it is incurred, if a reasonable estimate of fair value can be made. The liability is then accreted over time by applying an interest method of allocation to the liability. Substantially all accretion is related to regulated operations and is deferred pursuant to regulatory accounting. The present value of the liability is added to the carrying amount of the associated asset and this additional carrying amount is depreciated over the remaining life of the asset.

The present value of the initial obligation and subsequent updates are based on discounted cash flows, which include estimates regarding the timing of future cash flows, the selection of discount rates and cost escalation rates, among other factors. These underlying assumptions and estimates are made as of a point in time and are subject to change. The obligations for nuclear decommissioning are based on site-specific cost studies. Duke Energy Carolinas and Progress Energy Carolinas assume prompt dismantlement of the nuclear facilities, which reflects dismantling the site after operations are ceased. Progress Energy Florida assumes the nuclear facility will be placed into a safe storage configuration until the eventual dismantling of the site begins in approximately 40-60 years. The nuclear decommissioning asset retirement obligation also assumes Duke Energy Carolinas, Progress Energy Carolinas and Progress Energy Florida will store spent fuel on site until such time that it can be transferred to a U.S. Department of Energy (DOE) facility.

See Note 9 for further information.

Accounting For Risk Management, Hedging Activities And Financial Instruments

Accounting for Risk Management, Hedging Activities and Financial Instruments.

The Duke Energy Registrants may use a number of different derivative and non-derivative instruments in connection with their commodity price, interest rate and foreign currency risk management activities, including swaps, futures, forwards and options. All derivative instruments except those that qualify for the normal purchase/normal sale (NPNS) exception within the accounting guidance for derivatives are recorded on the Consolidated Balance Sheets at their fair value. The effective portion of the change in the fair value of derivative instruments designated as cash flow hedges is recorded in AOCI. The effective portion of the change in the fair value of a fair value hedge is offset in net income by changes in the hedged item. The Duke Energy Registrants may designate qualifying derivative instruments as either cash flow hedges or fair value hedges, while others either have not been designated as hedges or do not qualify as a hedge (hereinafter referred to as undesignated contracts).

For all contracts accounted for as a hedge, the Duke Energy Registrants prepare formal documentation of the hedge in accordance with the accounting guidance for derivatives. In addition, at inception and at least every three months thereafter, the Duke Energy Registrants formally assess whether the hedge contract is highly effective in offsetting changes in cash flows or fair values of hedged items. The Duke Energy Registrants document hedging activity by transaction type and risk management strategy.

See Note 15 for further information.

Unamortized Debt Premium, Discount And Expense

Unamortized Debt Premium, Discount and Expense.

Premiums, discounts and expenses incurred with the issuance of outstanding long-term debt are amortized over the terms of the debt issues. Any call premiums or unamortized expenses associated with refinancing higher-cost debt obligations used to finance regulated assets and operations are amortized consistent with regulatory treatment of those items, where appropriate. The amortization expense is recorded as a component of Interest Expense in the Consolidated Statements of Operations and is reflected as Depreciation, amortization and accretion within Net cash provided by operating activities on the Consolidated Statements of Cash Flows.

Pension And Other Post-Retirement Benefit Plans

Pension and Other Post-Retirement Benefit Plans.

Duke Energy maintains qualified, non-qualified and other post-retirement benefit plans. Eligible employees of the Subsidiary Registrants participate in the respective Duke Energy or Progress Energy qualified, non-qualified and other post-retirement benefit plans and are allocated their proportionate share of benefit costs.

See Note 23 for information related to Duke Energy's benefit plans, including certain accounting policies associated with these plans.

Guarantees

Guarantees.

Upon issuance or modification of a guarantee, the Duke Energy Registrants recognize a liability at the time of issuance or material modification for the estimated fair value of the obligation it assumes under that guarantee, if any. Fair value is estimated using a probability-weighted approach. The Duke Energy Registrants reduce the obligation over the term of the guarantee or related contract in a systematic and rational method as risk is reduced under the obligation. Any additional contingent loss for guarantee contracts subsequent to the initial recognition of a liability in accordance with applicable accounting guidance is accounted for and recognized at the time a loss is probable and the amount of the loss can be reasonably estimated.

The Duke Energy Registrants have entered into various indemnification agreements related to purchase and sale agreements and other types of contractual agreements with vendors and other third parties. These agreements typically cover environmental, tax, litigation and other matters, as well as breaches of representations, warranties and covenants. Typically, claims may be made by third parties for various periods of time, depending on the nature of the claim. Potential exposure under these indemnification agreements can range from a specified to an unlimited dollar amount, depending on the nature of the claim and the particular transaction.

See Note 7 for further information.

Accounting For Purchases And Sales Of Emission Allowances

Accounting For Purchases and Sales of Emission Allowances.

Emission allowances are issued by the Environmental Protection Agency (EPA) at zero cost and permit the holder of the allowance to emit certain gaseous by-products of fossil fuel combustion, including sulfur dioxide (SO2) and nitrogen oxide (NOx). Allowances may also be bought and sold via third-party transactions. Allowances allocated to or acquired by the Duke Energy Registrants are held primarily for consumption. Emission allowances at cost are included in Intangibles, net on the Consolidated Balance Sheets and the Duke Energy Registrants recognize expense as the allowances are consumed or sold. Gains or losses on sales of emission allowances by regulated businesses that do not provide for direct recovery through a cost-tracking mechanism and by nonregulated businesses are presented in Gains on Sales of Other Assets and Other, net, in the Consolidated Statements of Operations. For regulated businesses that provide for direct recovery of emission allowances, any gain or loss on sales of recoverable emission allowances are included in the rate structure of the regulated entity and are deferred as a regulatory asset or liability. Future rates charged to retail customers are impacted by any gain or loss on sales of recoverable emission allowances. Purchases and sales of emission allowances are presented gross as investing activities on the Consolidated Statements of Cash Flows. See Note 12 for discussion regarding the impairment of the carrying value of certain emission allowances in 2011.