Income Taxes (Deferred Taxes Rec - Details 2) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets and valuation allowance
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	35.00%	35.00%	35.00%
Deferred tax liabilities:
Deferred Tax Liabilities, Emissions Allowances	$ 30	$ 31
Derivatives, net	0	22
Cumulative translation adjustments	11	2
Investment in projects	(374)	(838)
Total deferred tax liabilities	415	893
Deferred tax assets:
Deferred compensation, accrued vacation and other reserves	318	255
Discount/premium on notes	45	68
Deferred Tax Assets, Property, Plant and Equipment	1,511	1,210
Deferred Tax Assets, Goodwill and Intangible Assets	83	39
Differences between book and tax basis of contracts	301	516
Pension and other postretirement benefits	183	218
Equity compensation	11	50
Bad debt reserve	12	6
U.S. capital loss carryforwards	1	1
U.S. Federal net operating loss carryforwards	1,171	1,373
Foreign net operating loss carryforwards	63	59
State net operating loss carryforwards	223	230
Foreign capital loss carryforwards	1	1
Deferred financing costs	4	6
Federal and state tax credit carryforwards	446	439
Federal benefit on state uncertain tax positions	12	17
Deferred Tax Assets, Intangibles	211	90
Deferred Tax Assets, Derivative Instruments	101	0
Deferred Tax Assets, Inventory	31	27
Deferred Tax Assets, Other	8	11
Total deferred tax assets	4,736	4,616
Valuation allowance	(4,116)	(3,575)
Total deferred tax assets, net of valuation allowance	620	1,041
Net deferred tax asset	205	148
NRG's net deferred tax position
Net deferred tax asset — noncurrent	225	167
Deferred Tax Liabilities, Net, Noncurrent	$ (20)	$ (19)