Condensed Consolidating Financial Information (Details 2) (USD $) In Millions	3 Months Ended					9 Months Ended
	Sep. 30, 2011		Jun. 30, 2011	Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010
Operating Revenues
Total operating revenues	$ 2,674			$ 2,685		$ 6,947		$ 7,033
Operating Costs and Expenses
Cost of operations	2,053			1,835		4,985		4,803
Depreciation and amortization	238			210		665		620
Impairment of Long-Lived Assets Held-for-use	160			0		160		0
Selling, general and administrative	169			172		479		441
Development costs	11			14		32		36
Total operating costs and expenses	2,631			2,231		6,321		5,900
Gain on sale of assets	0			0		0		23
Operating Income/(Loss)	43			454		626		1,156
Other Income/(Expense)
Equity in earnings/(losses) of consolidated subsidiaries	0			0		0		0
Equity in (losses)/earnings of unconsolidated affiliates	16			16		26		41
Impairment charge on investment	(3)		(11)	0		(495)		0
Other income, net	5			11		13		34
Loss on debt extinguishment	(32)			(1)		(175)		(2)
Interest expense	(164)			(168)		(504)		(467)
Total other (expense)/income	(178)			(142)		(1,135)		(394)
(Loss)/Income Before Income Taxes	(135)			312		(509)		762
Income tax (benefit)/expense	(80)			89		(815)		271
Net Income	(55)			223		306		491
Less: Net loss attributable to noncontrolling interest	0			0		0		(1)
Net Income/(Loss) attributable to NRG Energy, Inc.	(55)			223		306		492
Guarantor Subsidiaries
Operating Revenues
Total operating revenues	2,581			2,589		6,670		6,782
Operating Costs and Expenses
Cost of operations	1,993			1,775		4,791		4,631
Depreciation and amortization	224			198		626		590
Impairment of Long-Lived Assets Held-for-use	160					160
Selling, general and administrative	102			99		276		238
Development costs	0			0		0		0
Total operating costs and expenses	2,479			2,072		5,853		5,459
Gain on sale of assets								0
Operating Income/(Loss)	102			517		817		1,323
Other Income/(Expense)
Equity in earnings/(losses) of consolidated subsidiaries	6			8		21		30
Equity in (losses)/earnings of unconsolidated affiliates	2			4		8		5
Impairment charge on investment	(3)					(495)
Other income, net	3			1		3		4
Loss on debt extinguishment	0			0		0		0
Interest expense	(20)			1		(46)		(10)
Total other (expense)/income	(12)			14		(509)		29
(Loss)/Income Before Income Taxes	90			531		308		1,352
Income tax (benefit)/expense	11			178		123		479
Net Income						185		873
Less: Net loss attributable to noncontrolling interest								(1)
Net Income/(Loss) attributable to NRG Energy, Inc.	79			353		185		874
Non-Guarantor Subsidiaries
Operating Revenues
Total operating revenues	97			101		291		270
Operating Costs and Expenses
Cost of operations	63			65		194		184
Depreciation and amortization	10			9		28		23
Impairment of Long-Lived Assets Held-for-use	0					0
Selling, general and administrative	8			5		20		10
Development costs	0			2		(1)		8
Total operating costs and expenses	81			81		241		225
Gain on sale of assets								0
Operating Income/(Loss)	16			20		50		45
Other Income/(Expense)
Equity in earnings/(losses) of consolidated subsidiaries	4			0		(5)		0
Equity in (losses)/earnings of unconsolidated affiliates	14			12		18		36
Impairment charge on investment	0					0
Other income, net	1			6		6		23
Loss on debt extinguishment	0			0		0		(1)
Interest expense	(13)			(14)		(40)		(36)
Total other (expense)/income	6			4		(21)		22
(Loss)/Income Before Income Taxes	22			24		29		67
Income tax (benefit)/expense	3			4		6		20
Net Income						23		47
Less: Net loss attributable to noncontrolling interest								0
Net Income/(Loss) attributable to NRG Energy, Inc.	19			20		23		47
NRG Energy, Inc.
Operating Revenues
Total operating revenues	0			0		0		0
Operating Costs and Expenses
Cost of operations	(1)			0		5		7
Depreciation and amortization	4			3		11		7
Impairment of Long-Lived Assets Held-for-use	0					0
Selling, general and administrative	61			68		185		193
Development costs	11			12		33		28
Total operating costs and expenses	75			83		234		235
Gain on sale of assets								23
Operating Income/(Loss)	(75)			(83)		(234)		(212)
Other Income/(Expense)
Equity in earnings/(losses) of consolidated subsidiaries	88			365		185		891
Equity in (losses)/earnings of unconsolidated affiliates	0			0		0		0
Impairment charge on investment	0					0
Other income, net	1			4		4		7
Loss on debt extinguishment	(32)			(1)		(175)		(1)
Interest expense	(131)			(155)		(418)		(421)
Total other (expense)/income	(74)			213		(404)		476
(Loss)/Income Before Income Taxes	(149)			130		(638)		264
Income tax (benefit)/expense	(94)			(93)		(944)		(228)
Net Income						306		492
Less: Net loss attributable to noncontrolling interest								0
Net Income/(Loss) attributable to NRG Energy, Inc.	(55)			223		306		492
Eliminations
Operating Revenues
Total operating revenues	(4)	[1]		(5)	[1]	(14)	[1]	(19)	[1]
Operating Costs and Expenses
Cost of operations	(2)	[1]		(5)	[1]	(5)	[1]	(19)	[1]
Depreciation and amortization	0	[1]		0	[1]	0	[1]	0	[1]
Impairment of Long-Lived Assets Held-for-use	0	[1]				0	[1]
Selling, general and administrative	(2)	[1]		0	[1]	(2)	[1]	0	[1]
Development costs	0	[1]		0	[1]	0	[1]	0	[1]
Total operating costs and expenses	(4)	[1]		(5)	[1]	(7)	[1]	(19)	[1]
Gain on sale of assets								0	[1]
Operating Income/(Loss)	0	[1]		0	[1]	(7)	[1]	0	[1]
Other Income/(Expense)
Equity in earnings/(losses) of consolidated subsidiaries	(98)	[1]		(373)	[1]	(201)	[1]	(921)	[1]
Equity in (losses)/earnings of unconsolidated affiliates	0	[1]		0	[1]	0	[1]	0	[1]
Impairment charge on investment	0	[1]				0	[1]
Other income, net	0	[1]		0	[1]	0	[1]	0	[1]
Loss on debt extinguishment	0	[1]		0	[1]	0	[1]	0	[1]
Interest expense	0	[1]		0	[1]	0	[1]	0	[1]
Total other (expense)/income	(98)	[1]		(373)	[1]	(201)	[1]	(921)	[1]
(Loss)/Income Before Income Taxes	(98)	[1]		(373)	[1]	(208)	[1]	(921)	[1]
Income tax (benefit)/expense	0	[1]		0	[1]	0	[1]	0	[1]
Net Income						(208)	[1]	(921)	[1]
Less: Net loss attributable to noncontrolling interest								0	[1]
Net Income/(Loss) attributable to NRG Energy, Inc.	$ (98)	[1]		$ (373)	[1]	$ (208)	[1]	$ (921)	[1]

[1] All significant intercompany transactions have been eliminated in consolidation.