CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of Comprehensive Income [Abstract]
Net Income	$ 2,187	$ 510	$ 4,441
Other Comprehensive Income/(Loss), net of tax
Foreign currency translation adjustments, net of income tax	(5)	8	(1)
Available-for-sale securities, net of income tax	0	0	(19)
Defined benefit plans, net of income tax	85	(22)	(78)
Other comprehensive income/(loss)	80	(14)	(98)
Comprehensive Income	2,267	496	4,343
Less: Net income attributable to redeemable noncontrolling interest	0	0	3
Comprehensive Income Attributable to NRG Energy, Inc.	$ 2,267	$ 496	$ 4,340