Consolidated Statement of Stockholders' Equity - USD ($) $ in Millions	Total	Common Stock	Additional Paid-In Capital	Retained Earnings/ (Accumu-lated Deficit)	Treasury Stock	Accumulated Other Comprehensive Income/(Loss)	Noncontrolling Interest	NRG Yield	NRG Yield, Inc. [Member]	NRG Yield, Inc. [Member] Noncontrolling Interest
Balance at Dec. 31, 2013	$ 10,467	$ 4	$ 7,840	$ 3,695	$ (1,942)	$ 5	$ 865
Increase (Decrease) in Stockholders' Equity
Net (loss)/income attributable to NRG Energy, Inc.	134
Net income/(loss) attributable to noncontrolling interest	17
Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest	151
Other Comprehensive Income (Loss), Net of Tax	(189)					(179)
Issuance of shares for acquisition of EME	401		401
Noncontrolling Interest, Increase from Business Combination	352						352
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	(57)
Equity-based compensation	45		45
Purchase of treasury stock	(44)				(44)
Common stock dividends	(181)			(181)
Preferred Stock Dividends, Income Statement Impact	(56)
Redeemable Preferred Stock Dividends	9			(9)
ESPP share purchases	(1)			(4)	3
Proceeds from issuance of common stock	21		41				(41)	$ 0
Other Preferred Stock Dividends and Adjustments	(47)			47
Gain on Redemption of Redeemable Preferred Stock	0
Non-cash adjustment for issuance of convertible debt	23						23
Noncontrolling Interest, Increase from Subsidiary Equity Issuance	630						630
Noncontrolling Interest, Increase from Sale of Parent Equity Interest	125						125
Balance at Dec. 31, 2014	11,676	4	8,327	3,588	(1,983)	(174)	1,914
Increase (Decrease) in Stockholders' Equity
Net (loss)/income attributable to NRG Energy, Inc.	(6,382)
Net income/(loss) attributable to noncontrolling interest							(37)
Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest	(6,419)
Other Comprehensive Income (Loss), Net of Tax	1					1
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest							(4)
Other Comprehensive Income (Loss), Including OCI for NCI	(3)
Sale of Assets Under Common Control			(56)				83	27
Noncontrolling Interest, Increase from Business Combination							74	74
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	(159)
Equity-based compensation	24		26	(2)
Purchase of treasury stock	(437)				(437)
Common stock dividends	(191)			(191)
Preferred Stock Dividends, Income Statement Impact	(20)			20
ESPP share purchases	6		(1)		7
Noncontrolling Interest, Contributions from Noncontrolling Interest Holders	234						234
Proceeds from issuance of common stock	1
Other Preferred Stock Dividends and Adjustments	0
Gain on Redemption of Redeemable Preferred Stock	0
Non-cash adjustment for issuance of convertible debt	23						23
Noncontrolling Interest, Increase from Subsidiary Equity Issuance	599						599
Balance at Dec. 31, 2015	5,434	4	8,296	(3,007)	(2,413)	(173)	2,727
Increase (Decrease) in Stockholders' Equity
Net (loss)/income attributable to NRG Energy, Inc.	(774)
Net income/(loss) attributable to noncontrolling interest							(79)
Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest	(853)
Other Comprehensive Income (Loss), Net of Tax	38					38
Other Comprehensive Income (Loss), Including OCI for NCI	38
Sale of Assets Under Common Control			59				(16)	$ 43
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	(158)						(158)		$ (92)	$ (92)
Equity-based compensation	6		5	1
Common stock dividends	(74)			(74)
Preferred Stock Dividends, Income Statement Impact	(5)			5
ESPP share purchases	6		(2)	(6)	14
Noncontrolling Interest, Contributions from Noncontrolling Interest Holders	30						30
Proceeds from issuance of common stock	1
Other Preferred Stock Dividends and Adjustments	0
Gain on Redemption of Redeemable Preferred Stock	78			78
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests	(7)						(7)
Balance at Dec. 31, 2016	$ 4,446	$ 4	$ 8,358	$ (3,787)	$ (2,399)	$ (135)	$ 2,405