New Accounting Pronouncements	12 Months Ended
Dec. 31, 2017
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
New Accounting Pronouncements	NEW ACCOUNTING PRONOUNCEMENTS Recently Issued Pronouncements In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606), as amended. The objectives of this ASU are to improve upon revenue recognition requirements by providing a single comprehensive model to determine the measurement of revenue and timing of recognition. The core principle is that an entity will recognize revenue to depict the transfer of goods or services to customers at an amount that the entity expects to be entitled to in exchange for those goods or services. This ASU also requires expanded qualitative and quantitative disclosures regarding the nature, amount, timing, and uncertainty of revenues and cash flows arising from contracts with customers. The standard is to be applied retrospectively. The Registrants will adopt the standard effective January 1, 2018 using the modified retrospective approach. The Registrants have substantially completed the assessment of the amended ASU's impact, on their Consolidated Financial Statements. The ASU will not significantly affect the Registrants' financial position or results of operations. The Registrants will continue to monitor the impact of the ASU on existing revenue recognition internal controls, policies, and procedures. Industry-related issues being vetted through the final stages of the American Institute of Certified Public Accountants' Power and Utilities Industry Task Force process, which are not expected to have a significant impact on the Registrants, will continue to be monitored. The ASU will result in additional disclosures for revenue compared to the current guidance. Accordingly, the Registrants are evaluating information that would be useful for users of the Consolidated Financial Statements. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842), a replacement of Leases (Topic 840). This guidance requires a lessee to account for leases as finance or operating leases, and include disclosure of key information about leasing arrangements. Both types of leases will result in the lessee recognizing a right-of-use asset and a corresponding lease liability on its balance sheet, with differing methodology for income statement recognition. For lessors, the standard modifies the classification criteria and the accounting for sales-type and direct financing leases. Entities will classify leases to determine how to recognize lease-related revenue and expense. This standard is effective for public entities for fiscal years, and interim periods within those years, beginning after December 15, 2018, and early adoption is permitted. The Registrants do not plan to early adopt the standard. A modified retrospective approach is required for leases existing or entered into after the beginning of the earliest comparative period in the Consolidated Financial Statements, with certain practical expedients permitted. The Registrants expect an increase in assets and liabilities, as well as additional disclosures, however, they are currently assessing the impact of this ASU on their Consolidated Financial Statements. This assessment includes monitoring unresolved utility industry implementation guidance. The Registrants have conducted outreach activities across their lines of business and have begun implementation of a third-party software tool that will assist with the initial adoption and ongoing compliance. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments — Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. The amendments in this update replace the incurred loss impairment methodology in current generally accepted accounting principles with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. Entities will apply the new guidance as a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is adopted. The ASU is effective for the Registrants beginning after December 15, 2019, and interim periods therein. Early adoption is permitted. The Registrants are currently assessing the impact of this standard on their Consolidated Financial Statements. In March 2017, the FASB issued ASU No. 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 require that an employer report the service cost component in the same line item or items as other compensation costs arising from services rendered by the pertinent employees during the period. The other components of net benefit cost are required to be presented in the income statement separately from the service cost component and outside income from operations. The amendments in this update also allow only the service cost component to be eligible for capitalization when applicable. The standard will be applied retrospectively for the presentation of the service cost component and the other components of net periodic pension cost and net periodic postretirement benefit cost in the income statement and prospectively for the capitalization of the service cost component of net periodic pension cost and net periodic postretirement benefit in assets. The ASU is effective for the Registrants for fiscal years, and interim periods within those years, beginning after December 15, 2017, and early adoption is permitted. The Registrants will adopt the standard effective January 1, 2018. The components of net periodic benefit costs (credits) for pension benefits and other postretirement benefits are disclosed in Note 20 to the Consolidated Financial Statements, "Retirement Benefits and Trusteed Assets." The ASU will not have a significant impact on the Registrants' Consolidated Financial Statements. In February 2018, the FASB issued ASU No. 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. The amendments in this update allow a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the TCJA. The amendments in this update also require entities to disclose their accounting policy for releasing income tax effects from accumulated other comprehensive income. The ASU is effective for the Registrants for fiscal years beginning after December 15, 2018, and interim periods therein. Early adoption is permitted. The Registrants are currently assessing the impact of this standard on their Consolidated Financial Statements.

NEW ACCOUNTING PRONOUNCEMENTS

Recently Issued Pronouncements

In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606), as amended. The objectives of this ASU are to improve upon revenue recognition requirements by providing a single comprehensive model to determine the measurement of revenue and timing of recognition. The core principle is that an entity will recognize revenue to depict the transfer of goods or services to customers at an amount that the entity expects to be entitled to in exchange for those goods or services. This ASU also requires expanded qualitative and quantitative disclosures regarding the nature, amount, timing, and uncertainty of revenues and cash flows arising from contracts with customers. The standard is to be applied retrospectively. The Registrants will adopt the standard effective January 1, 2018 using the modified retrospective approach. The Registrants have substantially completed the assessment of the amended ASU's impact, on their Consolidated Financial Statements. The ASU will not significantly affect the Registrants' financial position or results of operations. The Registrants will continue to monitor the impact of the ASU on existing revenue recognition internal controls, policies, and procedures. Industry-related issues being vetted through the final stages of the American Institute of Certified Public Accountants' Power and Utilities Industry Task Force process, which are not expected to have a significant impact on the Registrants, will continue to be monitored. The ASU will result in additional disclosures for revenue compared to the current guidance. Accordingly, the Registrants are evaluating information that would be useful for users of the Consolidated Financial Statements.

In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842), a replacement of Leases (Topic 840). This guidance requires a lessee to account for leases as finance or operating leases, and include disclosure of key information about leasing arrangements. Both types of leases will result in the lessee recognizing a right-of-use asset and a corresponding lease liability on its balance sheet, with differing methodology for income statement recognition. For lessors, the standard modifies the classification criteria and the accounting for sales-type and direct financing leases. Entities will classify leases to determine how to recognize lease-related revenue and expense. This standard is effective for public entities for fiscal years, and interim periods within those years, beginning after December 15, 2018, and early adoption is permitted. The Registrants do not plan to early adopt the standard. A modified retrospective approach is required for leases existing or entered into after the beginning of the earliest comparative period in the Consolidated Financial Statements, with certain practical expedients permitted. The Registrants expect an increase in assets and liabilities, as well as additional disclosures, however, they are currently assessing the impact of this ASU on their Consolidated Financial Statements. This assessment includes monitoring unresolved utility industry implementation guidance. The Registrants have conducted outreach activities across their lines of business and have begun implementation of a third-party software tool that will assist with the initial adoption and ongoing compliance.

In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments — Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. The amendments in this update replace the incurred loss impairment methodology in current generally accepted accounting principles with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. Entities will apply the new guidance as a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is adopted. The ASU is effective for the Registrants beginning after December 15, 2019, and interim periods therein. Early adoption is permitted. The Registrants are currently assessing the impact of this standard on their Consolidated Financial Statements.

In March 2017, the FASB issued ASU No. 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 require that an employer report the service cost component in the same line item or items as other compensation costs arising from services rendered by the pertinent employees during the period. The other components of net benefit cost are required to be presented in the income statement separately from the service cost component and outside income from operations. The amendments in this update also allow only the service cost component to be eligible for capitalization when applicable. The standard will be applied retrospectively for the presentation of the service cost component and the other components of net periodic pension cost and net periodic postretirement benefit cost in the income statement and prospectively for the capitalization of the service cost component of net periodic pension cost and net periodic postretirement benefit in assets. The ASU is effective for the Registrants for fiscal years, and interim periods within those years, beginning after December 15, 2017, and early adoption is permitted. The Registrants will adopt the standard effective January 1, 2018. The components of net periodic benefit costs (credits) for pension benefits and other postretirement benefits are disclosed in Note 20 to the Consolidated Financial Statements, "Retirement Benefits and Trusteed Assets." The ASU will not have a significant impact on the Registrants' Consolidated Financial Statements.

In February 2018, the FASB issued ASU No. 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. The amendments in this update allow a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the TCJA. The amendments in this update also require entities to disclose their accounting policy for releasing income tax effects from accumulated other comprehensive income. The ASU is effective for the Registrants for fiscal years beginning after December 15, 2018, and interim periods therein. Early adoption is permitted. The Registrants are currently assessing the impact of this standard on their Consolidated Financial Statements.