Debt and Capital Leases Debt and Capital Leases (Details 3 - Sr Credit Facility & GenOn Sr Notes) $ in Millions		3 Months Ended					9 Months Ended
		Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)		Jun. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($)		Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Debt and Capital Leases
Debt Instrument, Description of Variable Rate Basis							3 month LIBOR
Loss on debt extinguishment, net			$ (50)			$ (2)	$ (119)		$ (9)
Debt and Capital Lease Obligations			19,422				19,422			$ 19,636
Long-term Debt			19,411				$ 19,411			19,620
Term Loan Facility Due 2023 [Member]
Debt and Capital Leases
Debt Instrument, Description of Variable Rate Basis							1 - month LIBOR
NRG Yield Revolving Credit Facility [Member]
Debt and Capital Leases
Line of Credit Facility, Fair Value of Amount Outstanding			0				$ 0
Recourse Debt [Member]
Debt and Capital Leases
Long-term Debt			8,168				8,168			8,584
Recourse Debt [Member] | Term Loan Facility Due 2023 [Member]
Debt and Capital Leases
Proceeds from Issuance of Senior Long-term Debt					$ 1,900
Percent of face value					99.50%
Debt Instrument, Periodic Payment, Percentage of Principal					0.0025
Loss on debt extinguishment, net					$ 21
Long-term Debt			$ 1,886				$ 1,886			0
Recourse Debt [Member] | Senior Notes due 2026 [Member]
Debt and Capital Leases
Proceeds from Issuance of Senior Long-term Debt					$ 1,000
Debt Instrument, Interest Rate, Stated Percentage			7.25%	[1]	7.25%		7.25%	[1]
Long-term Debt			$ 1,000				$ 1,000			0
Letter of Credit [Member] | NRG Yield Revolving Credit Facility [Member]
Debt and Capital Leases
Letters of Credit Outstanding, Amount			64				64
Non Recourse Debt [Member]
Debt and Capital Leases
Long-term Debt			11,243				11,243			11,036
Non Recourse Debt [Member] | NRG Yield Revolving Credit Facility [Member]
Debt and Capital Leases
Long-term Debt			0				$ 0			$ 306
London Interbank Offered Rate (LIBOR) [Member] | Recourse Debt [Member] | Term Loan Facility Due 2023 [Member]
Debt and Capital Leases
Debt Instrument, Description of Variable Rate Basis	[1]				LIBOR		LIBOR
Debt Instrument, Basis Spread on Variable Rate	[1]				2.75%		2.75%
London Interbank Offered Rate (LIBOR) [Member] | Revolving Credit Facility [Member]
Debt and Capital Leases
Debt Instrument, Description of Variable Rate Basis	[1]				LIBOR
Line of Credit Facility, Maximum Borrowing Capacity					$ 0
London Interbank Offered Rate (LIBOR) [Member] | Non Recourse Debt [Member] | NRG Yield Revolving Credit Facility [Member]
Debt and Capital Leases
Debt Instrument, Description of Variable Rate Basis	[1]						LIBOR
Debt Instrument, Basis Spread on Variable Rate	[1]						2.75%
London Interbank Offered Rate (LIBOR) floor [Member] | Recourse Debt [Member] | Term Loan Facility Due 2023 [Member]
Debt and Capital Leases
Debt Instrument, Description of Variable Rate Basis	[1]				LIBOR
Debt Instrument, Basis Spread on Variable Rate	[1]				0.75%
Subsequent Event [Member] | Non Recourse Debt [Member] | NRG Energy Center Minneapolis Series D Notes [Member]
Debt and Capital Leases
Proceeds from Issuance of Debt		$ 125
Debt Instrument, Interest Rate, Stated Percentage		3.55%
Subsequent Event [Member] | Shelf Facility [Member] | NRG Energy Center Minneapolis Series D Notes [Member]
Debt and Capital Leases
Long-term Debt		$ 70
GenOn Energy, Inc. [Member] | Senior Notes [Member] | Senior Unsecured Notes 2017 [Member]
Debt and Capital Leases
Debt and Capital Lease Obligations			$ 703				$ 703
2016 Tranche B Revolving Credit Facility due 2021 [Member] [Member] | Revolving Credit Facility [Member]
Debt and Capital Leases
Line of Credit Facility, Maximum Borrowing Capacity					$ 2,200
2016 Tranche A Revolving Credit Facility due 2018 [Member] | Revolving Credit Facility [Member]
Debt and Capital Leases
Line of Credit Facility, Maximum Borrowing Capacity					$ 289

[1] As of September 30, 2016, L+ equals 3 month LIBOR plus x%, with the exception of the Viento Funding II term loan, which is 6 month LIBOR plus x%, and the Alpine Term Loan, the NRG Marsh Landing term loan, the Walnut Creek term loan, and 2016 Term Loan Facility, which are 1 month LIBOR plus x%.