New Financial Accounting Standards (Policies)	3 Months Ended
Mar. 31, 2017
Accounting Changes and Error Corrections [Abstract]
New Financial Accounting Standards	New Financial Accounting Standards In May 2014, the Financial Accounting Standards Board (FASB) and the International Accounting Standards Board jointly issued a revenue recognition standard that will supersede the revenue recognition requirements within Accounting Standards Codification Topic 605, “Revenue Recognition,” and most industry-specific guidance under the Codification through Accounting Standards Update (ASU) No. 2014-09, “Revenue from Contracts with Customers (Topic 606).” The purpose of the new guidance is to create a consistent framework for revenue recognition. The guidance clarifies how to measure and recognize revenue arising from customer contracts to depict the transfer of goods or services in an amount that reflects the consideration the entity expects to receive. Amendments were issued subsequently to clarify key areas including principal/agent considerations, performance obligations, licensing, sales taxes, noncash consideration, and contracts. The new standard is effective for reporting periods beginning after December 15, 2017. Early adoption is permitted for reporting periods beginning after December 15, 2016, however, the Companies plan to adopt the new standard for reporting periods beginning after December 15, 2017. Under the new standard, companies may use either of the following transition methods: (i) a full retrospective approach reflecting the application of the standard in each prior reporting period with the option to elect certain practical expedients, or (ii) a modified retrospective approach with the cumulative effect of initially adopting ASU 2014-09 recognized at the date of adoption (which includes additional footnote disclosures). The Companies anticipate using the modified retrospective approach. The Companies are currently in the process of evaluating the impact of the new standard on their various revenue streams. The majority of the Companies’ sales are derived from tariffs to provide electric, gas, and steam service to customers. For such tariffs, the Companies expect that the revenue from contracts with the customer under ASU 2014-09 will be equivalent to the electricity, gas, or steam supplied in that period which is consistent with current practice. Consequently, the Companies do not anticipate that the new standard will significantly impact the amount and/or timing of such revenues. The Companies continue to review the potential impacts of other revenue at the Utilities and the Clean Energy Businesses on the Companies' financial position, results of operations and liquidity as well as the additional disclosures required under the new standard. In January 2017, the FASB issued amendments to the guidance for Business Combinations through ASU 2017-01, “Business Combinations (Topic 805): Clarifying the Definition of a Business.” The amendments in this update clarify the definition of a business and provide guidance on evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. For public entities, the amendments are effective for reporting periods beginning after December 15, 2017. Early adoption is permitted. The application of this guidance is not expected to have a material impact on the Companies’ financial position, results of operations and liquidity. In January 2017, the FASB issued amendments to the guidance for the subsequent measurement of goodwill through ASU 2017-04, “Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment.” The amendments in this update simplify goodwill impairment testing by eliminating Step 2 of the goodwill impairment test wherein an entity has to compute the implied fair value of goodwill by performing procedures to determine the fair value of its assets and liabilities. Under the new guidance, an entity should recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value up to the total amount of goodwill allocated to that reporting unit. For public entities, the amendments are effective for reporting periods beginning after December 15, 2019. Early adoption is permitted. The application of this guidance is not expected to have a material impact on the Companies’ financial position, results of operations and liquidity. In February 2017, the FASB issued amendments to the guidance for other income through ASU 2017-05, “Other Income-Gains and Losses from the Derecognition of Nonfinancial Assets (Subtopic 610-20): Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets.” The amendments in this update clarify the scope of assets within Subtopic 610-20 and add guidance for partial sales of nonfinancial assets. The amendments are effective upon the adoption of ASU 2014-09, and therefore will be effective for reporting periods beginning after December 15, 2017. The Company is in the process of evaluating the potential impact of the new guidance on the Company’s financial position, results of operations and liquidity. In March 2017, the FASB issued amendments to the guidance for retirement benefits through ASU 2017-07, “Compensation-Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost.” The amendments in this update modify the presentation of net benefit cost, where the service component must be disaggregated from the other components of net benefit cost and be presented in the same line item as current employee compensation costs. The remaining components of the net benefit cost should be presented outside of income from operations. Additionally, the update allows only the service cost component to be eligible for capitalization. For public entities, the amendments are effective for reporting periods beginning after December 15, 2017. Early adoption is permitted. The Companies are in the process of evaluating the potential impact of the new guidance on the Companies’ financial position, results of operations and liquidity. In March 2017, the FASB issued amendments to the guidance for debt securities through ASU 2017-08, “Receivables-Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities.” The amendments in this update shorten the amortization period for certain callable debt securities held at a premium. The amendments do not require an accounting change for securities held at a discount; the discount continues to be amortized to maturity. For public entities, the amendments are effective for reporting periods beginning after December 15, 2018. Early adoption is permitted. The application of this guidance is not expected to have a material impact on the Companies’ financial position, results of operations and liquidity.

New Financial Accounting Standards

In May 2014, the Financial Accounting Standards Board (FASB) and the International Accounting Standards Board jointly issued a revenue recognition standard that will supersede the revenue recognition requirements within Accounting Standards Codification Topic 605, “Revenue Recognition,” and most industry-specific guidance under the Codification through Accounting Standards Update (ASU) No. 2014-09, “Revenue from Contracts with Customers (Topic 606).” The purpose of the new guidance is to create a consistent framework for revenue recognition. The guidance clarifies how to measure and recognize revenue arising from customer contracts to depict the transfer of goods or services in an amount that reflects the consideration the entity expects to receive. Amendments were issued subsequently to clarify key areas including principal/agent considerations, performance obligations, licensing, sales taxes, noncash consideration, and contracts. The new standard is effective for reporting periods beginning after December 15, 2017. Early adoption is permitted for reporting periods beginning after December 15, 2016, however, the Companies plan to adopt the new standard for reporting periods beginning after December 15, 2017.

Under the new standard, companies may use either of the following transition methods: (i) a full retrospective approach reflecting the application of the standard in each prior reporting period with the option to elect certain practical expedients, or (ii) a modified retrospective approach with the cumulative effect of initially adopting ASU 2014-09 recognized at the date of adoption (which includes additional footnote disclosures). The Companies anticipate using the modified retrospective approach.

The Companies are currently in the process of evaluating the impact of the new standard on their various revenue streams. The majority of the Companies’ sales are derived from tariffs to provide electric, gas, and steam service to customers. For such tariffs, the Companies expect that the revenue from contracts with the customer under ASU 2014-09 will be equivalent to the electricity, gas, or steam supplied in that period which is consistent with current practice. Consequently, the Companies do not anticipate that the new standard will significantly impact the amount and/or timing of such revenues. The Companies continue to review the potential impacts of other revenue at the Utilities and the Clean Energy Businesses on the Companies' financial position, results of operations and liquidity as well as the additional disclosures required under the new standard.

In January 2017, the FASB issued amendments to the guidance for Business Combinations through ASU 2017-01, “Business Combinations (Topic 805): Clarifying the Definition of a Business.” The amendments in this update clarify the definition of a business and provide guidance on evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. For public entities, the amendments are effective for reporting periods beginning after December 15, 2017. Early adoption is permitted. The application of this guidance is not expected to have a material impact on the Companies’ financial position, results of operations and liquidity.

In January 2017, the FASB issued amendments to the guidance for the subsequent measurement of goodwill through ASU 2017-04, “Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment.” The amendments in this update simplify goodwill impairment testing by eliminating Step 2 of the goodwill impairment test wherein an entity has to compute the implied fair value of goodwill by performing procedures to determine the fair value of its assets and liabilities. Under the new guidance, an entity should recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value up to the total amount of goodwill allocated to that reporting unit. For public entities, the amendments are effective for reporting periods beginning after December 15, 2019. Early adoption is permitted. The application of this guidance is not expected to have a material impact on the Companies’ financial position, results of operations and liquidity.

In February 2017, the FASB issued amendments to the guidance for other income through ASU 2017-05, “Other Income-Gains and Losses from the Derecognition of Nonfinancial Assets (Subtopic 610-20): Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets.” The amendments in this update clarify the scope of assets within Subtopic 610-20 and add guidance for partial sales of nonfinancial assets. The amendments are effective upon the adoption of ASU 2014-09, and therefore will be effective for reporting periods beginning after December 15, 2017. The Company is in the process of evaluating the potential impact of the new guidance on the Company’s financial position, results of operations and liquidity.

In March 2017, the FASB issued amendments to the guidance for retirement benefits through ASU 2017-07, “Compensation-Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost.” The amendments in this update modify the presentation of net benefit cost, where the service component must be disaggregated from the other components of net benefit cost and be presented in the same line item as current employee compensation costs. The remaining components of the net benefit cost should be presented outside of income from operations. Additionally, the update allows only the service cost component to be eligible for capitalization. For public entities, the amendments are effective for reporting periods beginning after December 15, 2017. Early adoption is permitted. The Companies are in the process of evaluating the potential impact of the new guidance on the Companies’ financial position, results of operations and liquidity.

In March 2017, the FASB issued amendments to the guidance for debt securities through ASU 2017-08, “Receivables-Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities.” The amendments in this update shorten the amortization period for certain callable debt securities held at a premium. The amendments do not require an accounting change for securities held at a discount; the discount continues to be amortized to maturity. For public entities, the amendments are effective for reporting periods beginning after December 15, 2018. Early adoption is permitted. The application of this guidance is not expected to have a material impact on the Companies’ financial position, results of operations and liquidity.