Discontinued Operations and Dispositions - Discontinued Operations (Details)	Jun. 14, 2017 USD ($)	Jun. 12, 2017 USD ($) extension	Jun. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Long-term debt			$ 17,125,000,000	$ 16,703,000,000
GenOn Senior Notes Due in 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Interest rate, stated percentage			7.875%
Senior Notes Due In 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Interest rate, stated percentage			9.50%
GenOn Senior Notes Due in 2020
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Interest rate, stated percentage			9.875%
GenOn Americas Generation Senior Notes Due in 2021
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Interest rate, stated percentage			8.50%
GenOn Americas Generation Senior Notes Due in 2031
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Interest rate, stated percentage			9.125%
GenOn
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Pension liability			$ 119,000,000
Restructuring Support Agreement
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percentage of aggregate principal amount		93.00%
Intercompany secured revolving credit facility			125,000,000
Payment of pension contributions			13,000,000
Restructuring Support Agreement | GenOn
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Settlement consideration		$ 261,300,000
Estimated accumulated pension benefit obligation			119,000,000
Settlement Consideration | Restructuring Support Agreement | GenOn
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Accrued liabilities - affiliate			261,300,000
Services Agreement | GenOn
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Shared services, annualized rate		84,000,000
Credit applied		28,000,000
Services Agreement | Restructuring Support Agreement
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Shared services, annualized rate		$ 84,000,000
Monthly shared services	$ 5,000,000
Shared services, waived period		2 months
Shared services, number of extensions | extension		2
Shared services, extension period		1 month
Credit applied		$ 28,000,000
Services Agreement | Restructuring Support Agreement | GenOn
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Accrued liabilities - affiliate			28,000,000
Discontinued Operations | GenOn
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Long-term debt			2,500,000,000
GenOn
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cost method investment			$ 0