Debt and Capital Leases (NRG Recourse Debt 1 Issuances/Repurchases - Details 2) - USD ($) $ in Millions		3 Months Ended		12 Months Ended
		Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Debt Instrument
Loss on debt extinguishment				$ 142		$ (75)		$ 95
Senior notes, due 2020
Debt Instrument
Debt Instrument Repurchase, Accrued Interest				77		5
Loss on debt extinguishment				(117)		(19)
Deferred Financing Costs				$ 16		2
Recourse Debt | Senior Notes due 2026 [Member]
Debt Instrument
Proceeds from Issuance of Senior Long-term Debt			$ 1,000
Debt instrument, interest rate, stated percentage (as a percent)			7.25%	7.25%	[1]
Recourse Debt | Senior Notes due 2027 [Member]
Debt Instrument
Proceeds from Issuance of Senior Long-term Debt		$ 1,250
Debt instrument, interest rate, stated percentage (as a percent)		6.625%		6.625%	[1]
Recourse Debt | Senior notes, due 2020
Debt Instrument
Debt instrument, interest rate, stated percentage (as a percent)		8.25%		8.25%	[1]
Debt Instrument, Principal Amount Repurchased				$ 1,058		5
Debt Instrument, Repurchase Amount				$ 1,129	[2]	$ 5	[3]
Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed				(103.12%)		(96.50%)
Recourse Debt | Senior Notes 2024 [Member]
Debt Instrument
Debt instrument, interest rate, stated percentage (as a percent)	[1]			6.25%
Debt Instrument, Principal Amount Repurchased				$ 171		$ 95
Debt Instrument, Repurchase Amount				$ 163	[2]	$ 82	[3]
Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed				(94.52%)		(84.73%)
Recourse Debt | Senior notes, due 2022
Debt Instrument
Debt instrument, interest rate, stated percentage (as a percent)	[1]			6.25%
Debt Instrument, Principal Amount Repurchased				$ 108
Debt Instrument, Repurchase Amount	[2]			$ 105
Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed				(94.73%)
Recourse Debt | Senior notes, due 2020
Debt Instrument
Debt Instrument, Principal Amount Repurchased				$ 2,967		$ 246
Debt Instrument, Repurchase Amount				$ 3,145	[2]	231	[3]
Recourse Debt | Senior notes, due 2018
Debt Instrument
Debt instrument, interest rate, stated percentage (as a percent)	[1]			7.625%
Debt Instrument, Principal Amount Repurchased				$ 641	[4]	92
Debt Instrument, Repurchase Amount				$ 706	[2],[4]	$ 97	[3]
Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed				(107.89%)	[4]	(102.23%)
Redemptions by Cash				$ 186
Recourse Debt | Senior notes, due 2023
Debt Instrument
Debt instrument, interest rate, stated percentage (as a percent)	[1]			6.625%
Debt Instrument, Principal Amount Repurchased				$ 67		$ 54
Debt Instrument, Repurchase Amount				$ 64	[2]	$ 47	[3]
Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed				(94.13%)		(85.97%)
Recourse Debt | Senior Notes Due In 2021 [Member]
Debt Instrument
Debt instrument, interest rate, stated percentage (as a percent)		7.875%		7.875%	[1]
Debt Instrument, Principal Amount Repurchased	[5]			$ 922
Debt Instrument, Repurchase Amount	[2],[5]			$ 978
Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed	[5]			(104.00%)
Redemptions by Cash				$ 193

[1] As of December 31, 2016, L+ equals 3 month LIBOR plus x%, with the exception of the Viento term loan, which is 6 month LIBOR plus x% and the Alpine term loan, the NRG Marsh Landing term loan, the Walnut Creek loan, and 2023 Term Loan Facility, which are 1 month LIBOR plus x%.

[2] Includes payment for accrued interest.

[3] Includes payment for accrued interest.

[4] $186 million of the redemptions financed by cash on hand.

[5] $193 million of the redemptions financed by cash on hand.