Condensed Consolidated Statements of Comprehensive Loss Income (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Net income	$ 8	$ (55)	$ 61	$ 306
Other comprehensive (loss)/income, net of tax
Unrealized loss on derivatives, net of income tax benefit of $24, $45, $76, and $131	(43)	(76)	(132)	(225)
Foreign currency translation adjustments, net of income tax benefit of $0, $16, $1, and $4	1	(27)	(1)	(5)
Reclassification adjustment for translation gain realized upon sale of Schkopau, net of income tax benefit of $6, $0, $6, and $0	(11)	0	(11)	0
Available-for-sale Securities, net of tax, tax benefit/(expense) of $(1), $1, $(1), and $1	2	(1)	2	(2)
Defined benefit plans	0	0	0	1
Other comprehensive loss	(51)	(104)	(142)	(231)
Comprehensive (loss)/income	(43)	(159)	(81)	75
Comprehensive Income attributable to noncontrolling interest	9	0	18	0
Comprehensive (loss)/income attributable to NRG Energy, Inc.	(52)	(159)	(99)	75
Dividends for preferred shares	2	2	7	7
Comprehensive (loss)/income available for common stockholders	$ (54)	$ (161)	$ (106)	$ 68