Summary of Significant Accounting Policies - Noncontrolling Interest (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Noncontrolling Interest [Roll Forward]
Balance as of beginning of period			$ 2,405
Dividends paid to NRG Yield, Inc. public shareholders			(52)
Distributions to noncontrolling interest			(39)
Comprehensive loss attributable to noncontrolling interest	$ (17)	$ (16)	(56)	$ (68)
Contributions from noncontrolling interest			76
Sale of assets to NRG Yield, Inc.			3
Balance as of end of period	$ 2,462		2,462
Noncontrolling Interest
Noncontrolling Interest [Roll Forward]
Comprehensive loss attributable to noncontrolling interest			(19)
Non-cash adjustments to noncontrolling interest			$ 88