Debt and Capital Leases (NRG Non-Recourse Debt 1 - GenOn Sr Notes) (Details 5) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Debt Instrument
Amount of Restricted Net Assets for Consolidated and Unconsolidated Subsidiaries		$ 4,900
Long-term Debt		19,406	$ 19,620
Gain (Loss) on Extinguishment of Debt		$ (142)	75	$ (95)
GenOn Senior Notes [Member]
Debt Instrument
Debt Instrument, Principal Amount Repurchased			(119)
Debt Instrument, Repurchase Amount			108
Redemption Period Prior To 15 January 2018 [Member] | GenOn senior notes, due 2018
Debt Instrument
Debt Instrument, Redemption, Description		Prior to maturity, GenOn may redeem the senior notes due 2018, in whole or in part, at a redemption price equal to 100% of the principal amount plus a premium and accrued and unpaid interest. The premium is the greater of: (i) 1% of the principal amount of the notes; or (ii) the excess of the following: the present value of 100% of the note, plus interest payments due on the note through maturity, discounted at a Treasury rate plus 0.50% over the principal amount of the note.
Redemption Period From October 15, 2016 to October 14, 2017 [Member] | GenOn senior notes, due 2020
Debt Instrument
Debt Instrument, Redemption Price, Percentage		103.292%
Redemption Period From October 15, 2017 to October 14, 2018 [Member] | GenOn senior notes, due 2020
Debt Instrument
Debt Instrument, Redemption Price, Percentage		101.646%
Redemption Period Beginning with October 15, 2018 [Member] | GenOn senior notes, due 2020
Debt Instrument
Debt Instrument, Redemption Price, Percentage		100.00%
Redemption Period Prior to Maturity [Member] | GenOn Senior Notes Due in 2017 [Member]
Debt Instrument
Debt Instrument, Redemption, Description		Prior to maturity, GenOn may redeem all or a part of the GenOn Senior Notes due 2017 at a redemption price equal to 100% of the notes plus a premium and accrued and unpaid interest. The premium is the greater of: (i) 1% of the principal amount of the notes; or (ii) the excess of the following: the present value of 100% of the note, plus interest payments due on the note through maturity, discounted at a Treasury rate plus 0.50% over the principal amount of the note
GenOn Energy [Member]
Debt Instrument
Restricted Payments Limit		$ 250
Other Restricted Assets		368
Non Recourse Debt [Member]
Debt Instrument
Long-term Debt		11,620	11,036
Non Recourse Debt [Member] | GenOn Senior Notes [Member]
Debt Instrument
Long-term Debt		1,911	1,956
Debt Instrument, Principal Amount Repurchased			(119)
Gain (Loss) on Extinguishment of Debt			23
Non Recourse Debt [Member] | GenOn senior notes, due 2018
Debt Instrument
Long-term Debt		$ 687	708
Debt Instrument, Interest Rate, Stated Percentage	[1]	9.50%
Debt Instrument, Principal Amount Repurchased			$ (25)
Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed			90.95%
Gain (Loss) on Extinguishment of Debt			$ 5
Non Recourse Debt [Member] | GenOn senior notes, due 2020
Debt Instrument
Long-term Debt		$ 525	534
Debt Instrument, Interest Rate, Stated Percentage	[1]	9.875%
Debt Instrument, Principal Amount Repurchased			$ (61)
Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed			83.847%
Gain (Loss) on Extinguishment of Debt			$ 15
Non Recourse Debt [Member] | GenOn Senior Notes Due in 2017 [Member]
Debt Instrument
Long-term Debt		$ 699	714
Debt Instrument, Interest Rate, Stated Percentage	[1]	7.875%
Debt Instrument, Principal Amount Repurchased			$ (33)
Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed			95.172%
Gain (Loss) on Extinguishment of Debt			$ 3

[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%.