New Accounting Standards	12 Months Ended
Dec. 31, 2017
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
New Accounting Pronouncements and Changes in Accounting Principles	New Accounting Standards In March 2016, the FASB issued Accounting Standards Update ("ASU") 2016-09, Compensation - Stock Compensation (Topic 718) Improvements to Employee Share-Based Payment Accounting to simplify the accounting for share-based payment transactions, including the income tax consequences, classification of awards either as equity or liabilities, and classification on the statements of cash flows. The Company adopted the new standard effective January 1, 2017. The adoption of the new standard did not have a material impact on the Company's financial condition, results of operations or cash flows. The cumulative effect of the adoption of the new standard was to increase net operating loss carryforward deferred tax assets and retained earnings by $0.2 million on January 1, 2017. In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) to provide a framework that replaces the existing revenue recognition guidance, and has since modified the standard with several ASUs. The standard provides that an entity should recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. More specifically, the standard requires entities to recognize revenue through the application of a five-step model, which includes the: (i) identification of the contract; (ii) identification of the performance obligations; (iii) determination of the transaction price; (iv) allocation of the transaction price to the performance obligations; and (v) the recognition of revenue as the entity satisfies the performance obligations. The Company will adopt the new standard for reporting periods beginning on January 1, 2018, and intends use the modified retrospective approach. The Company has analyzed the impact of the new standard on its various revenue and cash flow streams, and the impact on changes to business processes, systems and controls to support recognition under the new guidance. Tariff sales to customers are determined to be in the scope of the new standard and represent a significant portion of the Company’s total operating revenues. The Company has determined that the timing or pattern of revenue recognition from tariff sales will not change. Implementation of the new standard will also not significantly change the timing or pattern of revenue recognition from other revenue streams. Upon adoption of the standard, the Company expects its disclosures to disaggregate revenues primarily by tariff based categories and off-system sales. In January 2016, the FASB issued ASU 2016-01, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Liabilities to enhance the reporting model for financial instruments by addressing certain aspects of recognition, measurement, presentation, and disclosure. ASU 2016-01 generally requires entities to measure equity investments that do not result in consolidation and are not accounted for under the equity method at fair value and recognize any changes in fair value in net income. The guidance for classifying and measuring investments in debt securities and loans is not changed by this ASU, but requires entities to record changes in other comprehensive income. Financial assets and financial liabilities must be separately presented by measurement category on the balance sheet or in the accompanying notes to the financial statements. ASU 2016-01 clarifies the need for a valuation allowance on a deferred tax asset related to available-for-sale securities in combination with the entity's other deferred tax assets. The provisions of this ASU become effective for reporting periods beginning after December 15, 2017. Upon adoption of the new standard, the Company expects to record the cumulative effects as of January 1, 2018 which will result in a net reduction to accumulated other comprehensive income of $41.0 million, net of tax, and a corresponding increase in retained earnings for unrealized gains (losses) related to equity securities owned by the Company. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and requiring qualitative and quantitative disclosures on leasing agreements. ASU 2016-02 maintains a distinction between finance leases and operating leases similar to the distinction under previous leases guidance for capital leases and operating leases. The impact of leases reported in the Company's operating results and statement of cash flows are expected to be similar to previous GAAP. ASU 2016-02 requires the recognition in the statement of financial position, by the lessee, of a liability to make lease payments (the lease liability) and a right-of-use asset representing its right to use the underlying asset for the lease term. How leases are recorded in regard to financial position represents a significant change from previous GAAP guidance. The lessee is permitted to make an accounting policy election to not recognize lease assets and lease liabilities for short-term leases. Implementation of the standard will be required for reporting periods beginning after December 15, 2018. Adoption of the new lease accounting standard will require the Company to apply the new standard to the earliest period using a modified retrospective approach. The Company is currently in the process of evaluating the impact of the new standard, which includes continuing to monitor activities of the FASB, including the impact of the recently issued ASU 2018-01, and the proposed project to allow entities to adopt the standard with a cumulative effect adjustment as of the beginning of the adoption year, while maintaining prior year comparative financial information and disclosures as reported. ASU 2018-01, Land Easement Practical expedient for Transition to Topic 842, provides an optional practical expedient to not evaluate existing or expired land easements under Topic 842, if those land easements were not previously accounted for as leases under Accounting Standards Codification ("ASC") Topic 840. The Company currently anticipates that it will apply the practical expedient under ASU 2018-01 to its existing or expired land easements as part of its transition to Topic 842. The Company's evaluation process also includes evaluating the impact, if any, on changes to business processes, systems and controls to support recognition and disclosure under the new guidance; however, at this time the Company is unable to determine the impact this standard will have on the financial statements and related disclosures. In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326). ASU 2016-13 changes how companies measure and recognize credit impairment for many financial assets. The new current expected credit loss model will require companies to immediately recognize an estimate of credit losses expected to occur over the remaining life of the financial assets that are in the scope of the standard. The ASU also makes targeted amendments to the current impairment model for available-for-sale debt securities. The provisions of ASU 2016-13 will be required for reporting periods beginning after December 15, 2019. ASU 2016-13 will be applied in a modified retrospective approach through a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is implemented. The Company is currently assessing the future impact of ASU 2016-13. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230) Classification of Certain Cash Receipts and Cash Payments to reduce diversity in practice in how certain cash receipts and cash payments are classified in the statement of cash flows. The provisions of ASU 2016-15 will be required for reporting periods beginning after December 15, 2017. ASU 2016-15 will be applied using a retrospective transition method to each period presented. If it is impracticable to apply ASU 2016-15 retrospectively for some of the issues, the amendments for those issues may be applied prospectively as of the earliest date practicable. The Company is currently assessing the future impact of this ASU. In March 2017, the FASB issued ASU 2017-07, Compensation - Retirement Benefits (Topic 715) Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost. ASU 2017-07 amends Accounting Standards Codification 715, Compensation - Retirement Benefits, to require companies to present the service cost component of net benefit cost in the income statement line items where compensation cost is reported. Companies will present all other components of net benefit cost separately from the line item(s) that includes the service cost and outside of any subtotal of operating income. In addition, only the service cost component will be eligible for capitalization in assets. The amendments in ASU 2017-07 will be required for reporting periods beginning after December 15, 2017. The amendments in ASU 2017-07 should be applied retrospectively for the income statement presentation of the service cost component and the other components of net benefit costs and prospectively, on and after the effective date, for the capitalization of the service cost component. The Company expects that the retrospective impact of implementing this ASU on the Statement of Operations for the twelve months ended December 31, 2017 would be an increase in (i) Other operations of $8.2 million, (ii) Other interest of $15.8 million, (iii) Miscellaneous non-operating income of $32.4 million, and (iv) Miscellaneous non-operating deductions of $8.4 million. In May 2017, the FASB issued ASU 2017-09, Compensation - Stock Compensation (Topic 718), Scope of Modification Accounting, to provide guidance about when to account for a change to the terms or conditions of a share-based payment award as a modification. Under ASU 2017-09, modification accounting is required only if the fair value, the vesting conditions, or the classification of the award (as equity or liability) changes as a result of the change in terms or conditions. The amendments of ASU 2017-09 will be required for reporting periods beginning after December 15, 2017. ASU 2017-09 should be applied prospectively to an award modified on or after the adoption date. The Company is assessing the future impact of ASU 2017-09; however, it currently does not expect the impact of this ASU to be significant to the Company's financial conditions, results of operations or cash flows. In February 2018, the FASB issued ASU 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220) as a result of concerns raised by stakeholders due to the TCJA. More specifically, the concerns raised are that because the adjustment due to the reduction of the historical corporate income tax rate of 35% to the newly enacted corporate income tax rate of 21% is required to be made for accumulated deferred income taxes, the tax effect of items within accumulated other comprehensive income (“AOCI”) do not reflect the appropriate tax rate under current accounting standards which would result in "stranded taxes". ASU 2018-02 allows companies to reclassify stranded taxes from AOCI to retained earnings. The amount of the reclassification would be the difference between the historical corporate income tax rate of 35% and the newly enacted 21% corporate income tax rate. The provisions of ASU 2018-02 are effective for fiscal years and interim periods within that reporting period beginning after December 15, 2018. Early adoption is permitted, including adoption in any interim periods for reporting periods for which financial statements have not been issued. The Company is currently in the process of evaluating the impact of ASU 2018-02 and its impact on regulated utilities. At December 31, 2017, the Company has $7.2 million in stranded taxes in AOCI.

New Accounting Standards

In March 2016, the FASB issued Accounting Standards Update ("ASU") 2016-09, Compensation - Stock Compensation (Topic 718) Improvements to Employee Share-Based Payment Accounting to simplify the accounting for share-based payment transactions, including the income tax consequences, classification of awards either as equity or liabilities, and classification on the statements of cash flows. The Company adopted the new standard effective January 1, 2017. The adoption of the new standard did not have a material impact on the Company's financial condition, results of operations or cash flows. The cumulative effect of the adoption of the new standard was to increase net operating loss carryforward deferred tax assets and retained earnings by $0.2 million on January 1, 2017.

In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) to provide a framework that replaces the existing revenue recognition guidance, and has since modified the standard with several ASUs. The standard provides that an entity should recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. More specifically, the standard requires entities to recognize revenue through the application of a five-step model, which includes the: (i) identification of the contract; (ii) identification of the performance obligations; (iii) determination of the transaction price; (iv) allocation of the transaction price to the performance obligations; and (v) the recognition of revenue as the entity satisfies the performance obligations. The Company will adopt the new standard for reporting periods beginning on January 1, 2018, and intends use the modified retrospective approach.

The Company has analyzed the impact of the new standard on its various revenue and cash flow streams, and the impact on changes to business processes, systems and controls to support recognition under the new guidance. Tariff sales to customers are determined to be in the scope of the new standard and represent a significant portion of the Company’s total operating revenues. The Company has determined that the timing or pattern of revenue recognition from tariff sales will not change. Implementation of the new standard will also not significantly change the timing or pattern of revenue recognition from other revenue streams. Upon adoption of the standard, the Company expects its disclosures to disaggregate revenues primarily by tariff based categories and off-system sales.

In January 2016, the FASB issued ASU 2016-01, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Liabilities to enhance the reporting model for financial instruments by addressing certain aspects of recognition, measurement, presentation, and disclosure. ASU 2016-01 generally requires entities to measure equity investments that do not result in consolidation and are not accounted for under the equity method at fair value and recognize any changes in fair value in net income. The guidance for classifying and measuring investments in debt securities and loans is not changed by this ASU, but requires entities to record changes in other comprehensive income. Financial assets and financial liabilities must be separately presented by measurement category on the balance sheet or in the accompanying notes to the financial statements. ASU 2016-01 clarifies the need for a valuation allowance on a deferred tax asset related to available-for-sale securities in combination with the entity's other deferred tax assets. The provisions of this ASU become effective for reporting periods beginning after December 15, 2017. Upon adoption of the new standard, the Company expects to record the cumulative effects as of January 1, 2018 which will result in a net reduction to accumulated other comprehensive income of $41.0 million, net of tax, and a corresponding increase in retained earnings for unrealized gains (losses) related to equity securities owned by the Company.

In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and requiring qualitative and quantitative disclosures on leasing agreements. ASU 2016-02 maintains a distinction between finance leases and operating leases similar to the distinction under previous leases guidance for capital leases and operating leases. The impact of leases reported in the Company's operating results and statement of cash flows are expected to be similar to previous GAAP. ASU 2016-02 requires the recognition in the statement of financial position, by the lessee, of a liability to make lease payments (the lease liability) and a right-of-use asset representing its right to use the underlying asset for the lease term. How leases are recorded in regard to financial position represents a significant change from previous GAAP guidance. The lessee is permitted to make an accounting policy election to not recognize lease assets and lease liabilities for short-term leases. Implementation of the standard will be required for reporting periods beginning after December 15, 2018. Adoption of the new lease accounting standard will require the Company to apply the new standard to the earliest period using a modified retrospective approach. The Company is currently in the process of evaluating the impact of the new standard, which includes continuing to monitor activities of the FASB, including the impact of the recently issued ASU 2018-01, and the proposed project to allow entities to adopt the standard with a cumulative effect adjustment as of the beginning of the adoption year, while maintaining prior year comparative financial information and disclosures as reported. ASU 2018-01, Land Easement Practical expedient for Transition to Topic 842, provides an optional practical expedient to not evaluate existing or expired land easements under Topic 842, if those land easements were not previously accounted for as leases under Accounting Standards Codification ("ASC") Topic 840. The Company currently anticipates that it will apply the practical expedient under ASU 2018-01 to its existing or expired land easements as part of its transition to Topic 842. The Company's evaluation process also includes evaluating the impact, if any, on changes to business processes, systems and controls to support recognition and disclosure under the new guidance; however, at this time the Company is unable to determine the impact this standard will have on the financial statements and related disclosures.

In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326). ASU 2016-13 changes how companies measure and recognize credit impairment for many financial assets. The new current expected credit loss model will require companies to immediately recognize an estimate of credit losses expected to occur over the remaining life of the financial assets that are in the scope of the standard. The ASU also makes targeted amendments to the current impairment model for available-for-sale debt securities. The provisions of ASU 2016-13 will be required for reporting periods beginning after December 15, 2019. ASU 2016-13 will be applied in a modified retrospective approach through a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is implemented. The Company is currently assessing the future impact of ASU 2016-13.

In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230) Classification of Certain Cash Receipts and Cash Payments to reduce diversity in practice in how certain cash receipts and cash payments are classified in the statement of cash flows. The provisions of ASU 2016-15 will be required for reporting periods beginning after December 15, 2017. ASU 2016-15 will be applied using a retrospective transition method to each period presented. If it is impracticable to apply ASU 2016-15 retrospectively for some of the issues, the amendments for those issues may be applied prospectively as of the earliest date practicable. The Company is currently assessing the future impact of this ASU.

In March 2017, the FASB issued ASU 2017-07, Compensation - Retirement Benefits (Topic 715) Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost. ASU 2017-07 amends Accounting Standards Codification 715, Compensation - Retirement Benefits, to require companies to present the service cost component of net benefit cost in the income statement line items where compensation cost is reported. Companies will present all other components of net benefit cost separately from the line item(s) that includes the service cost and outside of any subtotal of operating income. In addition, only the service cost component will be eligible for capitalization in assets. The amendments in ASU 2017-07 will be required for reporting periods beginning after December 15, 2017. The amendments in ASU 2017-07 should be applied retrospectively for the income statement presentation of the service cost component and the other components of net benefit costs and prospectively, on and after the effective date, for the capitalization of the service cost component. The Company expects that the retrospective impact of implementing this ASU on the Statement of Operations for the twelve months ended December 31, 2017 would be an increase in (i) Other operations of $8.2 million, (ii) Other interest of $15.8 million, (iii) Miscellaneous non-operating income of $32.4 million, and (iv) Miscellaneous non-operating deductions of $8.4 million.

In May 2017, the FASB issued ASU 2017-09, Compensation - Stock Compensation (Topic 718), Scope of Modification Accounting, to provide guidance about when to account for a change to the terms or conditions of a share-based payment award as a modification. Under ASU 2017-09, modification accounting is required only if the fair value, the vesting conditions, or the classification of the award (as equity or liability) changes as a result of the change in terms or conditions. The amendments of ASU 2017-09 will be required for reporting periods beginning after December 15, 2017. ASU 2017-09 should be applied prospectively to an award modified on or after the adoption date. The Company is assessing the future impact of ASU 2017-09; however, it currently does not expect the impact of this ASU to be significant to the Company's financial conditions, results of operations or cash flows.

In February 2018, the FASB issued ASU 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220) as a result of concerns raised by stakeholders due to the TCJA. More specifically, the concerns raised are that because the adjustment due to the reduction of the historical corporate income tax rate of 35% to the newly enacted corporate income tax rate of 21% is required to be made for accumulated deferred income taxes, the tax effect of items within accumulated other comprehensive income (“AOCI”) do not reflect the appropriate tax rate under current accounting standards which would result in "stranded taxes". ASU 2018-02 allows companies to reclassify stranded taxes from AOCI to retained earnings. The amount of the reclassification would be the difference between the historical corporate income tax rate of 35% and the newly enacted 21% corporate income tax rate. The provisions of ASU 2018-02 are effective for fiscal years and interim periods within that reporting period beginning after December 15, 2018. Early adoption is permitted, including adoption in any interim periods for reporting periods for which financial statements have not been issued. The Company is currently in the process of evaluating the impact of ASU 2018-02 and its impact on regulated utilities. At December 31, 2017, the Company has $7.2 million in stranded taxes in AOCI.