Condensed Consolidating Financial Information - Balance Sheets (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current Assets
Cash and cash equivalents	$ 991	$ 938	$ 853
Funds deposited by counterparties	37	2	55
Restricted cash	508	446	414
Accounts receivable - trade	1,079	1,058
Inventory	532	721
Derivative instruments	626	1,067
Cash collateral posted in support of energy risk management activities	171	150
Accounts receivable - affiliate	95	114
Current assets held-for-sale	115	9
Prepayments and other current assets	261	290
Current assets - discontinued operations	0	1,919
Total current assets	4,415	6,714
Net Property, Plant and Equipment	13,908	15,369
Other Assets
Investment in subsidiaries	0	0
Equity investments in affiliates	1,038	1,120
Notes receivable, less current portion	2	16
Goodwill	539	662
Intangible assets, net	1,746	1,973
Nuclear decommissioning trust fund	692	610
Deferred income taxes	134	225
Derivative instruments	172	181
Non-current assets held-for-sale	43	10
Other non-current assets	629	841
Non-current assets - discontinued operations	0	2,961
Total other assets	4,995	8,599
Total Assets	23,318	30,682
Current Liabilities
Current portion of long-term debt and capital leases	688	516
Accounts payable	881	782
Accounts payable - affiliate	33	31
Derivative instruments	555	1,092
Cash collateral received in support of energy risk management activities	37	81
Accrued interest expense	156	180
Current liabilities - held for sale	72	0
Other accrued expenses and other current liabilities	734	810
Other accrued expenses and other current liabilities - affiliate	161	0
Current liabilities - discontinued operations	0	1,210
Total current liabilities	3,317	4,702
Other Liabilities
Long-term debt and capital leases	15,716	15,957
Nuclear decommissioning reserve	269	287
Nuclear decommissioning trust liability	415	339
Postretirement and other benefit obligations	458	510
Deferred income taxes	21	20
Derivative instruments	197	284
Out-of-market contracts, net	207	230
Non-current liabilities held-for-sale	8	11
Other non-current liabilities	664	666
Non-current liabilities - discontinued operations	0	3,184
Total non-current liabilities	17,955	21,488
Total Liabilities	21,272	26,190
Redeemable noncontrolling interest in subsidiaries	78	46	29	$ 19
Total Stockholders' Equity	1,968	4,446	$ 5,434	$ 11,676
Total Liabilities and Stockholders' Equity	23,318	30,682
Eliminations
Current Assets
Cash and cash equivalents	0	0
Funds deposited by counterparties	0	0
Restricted cash	0	0
Accounts receivable - trade	0	0
Inventory	0	0
Derivative instruments	(88)	(92)
Cash collateral posted in support of energy risk management activities	0	0
Accounts receivable - affiliate	(698)	(139)
Current assets held-for-sale	0	0
Prepayments and other current assets	0	0
Current assets - discontinued operations		0
Total current assets	(786)	(231)
Net Property, Plant and Equipment	(26)	(27)
Other Assets
Investment in subsidiaries	(7,503)	(11,363)
Equity investments in affiliates	0	0
Notes receivable, less current portion	(36)	76
Goodwill	0	0
Intangible assets, net	(3)	(3)
Nuclear decommissioning trust fund	0	0
Deferred income taxes	0	0
Derivative instruments	(20)	(43)
Non-current assets held-for-sale	0	0
Other non-current assets	0	0
Non-current assets - discontinued operations		0
Total other assets	(7,562)	(11,333)
Total Assets	(8,374)	(11,591)
Current Liabilities
Current portion of long-term debt and capital leases	(36)	76
Accounts payable	0	0
Accounts payable - affiliate	(698)	(79)
Derivative instruments	(88)	(92)
Cash collateral received in support of energy risk management activities	0	0
Accrued interest expense	0	0
Current liabilities - held for sale	0
Other accrued expenses and other current liabilities	0	0
Other accrued expenses and other current liabilities - affiliate	0
Current liabilities - discontinued operations		0
Total current liabilities	(822)	(95)
Other Liabilities
Long-term debt and capital leases	0	0
Nuclear decommissioning reserve	0	0
Nuclear decommissioning trust liability	0	0
Postretirement and other benefit obligations	0	0
Deferred income taxes	0	0
Derivative instruments	(20)	(43)
Out-of-market contracts, net	0	0
Non-current liabilities held-for-sale	0	0
Other non-current liabilities	0	0
Non-current liabilities - discontinued operations		0
Total non-current liabilities	(20)	(43)
Total Liabilities	(842)	(138)
Redeemable noncontrolling interest in subsidiaries	0	0
Total Stockholders' Equity	(7,532)	(11,453)
Total Liabilities and Stockholders' Equity	(8,374)	(11,591)
Guarantor Subsidiaries
Current Assets
Cash and cash equivalents	0	0
Funds deposited by counterparties	37	2
Restricted cash	4	11
Accounts receivable - trade	769	734
Inventory	339	482
Derivative instruments	625	962
Cash collateral posted in support of energy risk management activities	170	116
Accounts receivable - affiliate	712	307
Current assets held-for-sale	8	0
Prepayments and other current assets	116	76
Current assets - discontinued operations		0
Total current assets	2,780	2,690
Net Property, Plant and Equipment	2,527	4,219
Other Assets
Investment in subsidiaries	(106)	1,090
Equity investments in affiliates	0	(13)
Notes receivable, less current portion	0	0
Goodwill	360	359
Intangible assets, net	458	592
Nuclear decommissioning trust fund	692	610
Deferred income taxes	377	3
Derivative instruments	121	144
Non-current assets held-for-sale	0	0
Other non-current assets	51	67
Non-current assets - discontinued operations		0
Total other assets	1,953	2,852
Total Assets	7,260	9,761
Current Liabilities
Current portion of long-term debt and capital leases	0	0
Accounts payable	546	501
Accounts payable - affiliate	752	753
Derivative instruments	535	947
Cash collateral received in support of energy risk management activities	37	81
Accrued interest expense	3	3
Current liabilities - held for sale	0
Other accrued expenses and other current liabilities	288	313
Other accrued expenses and other current liabilities - affiliate	0
Current liabilities - discontinued operations		0
Total current liabilities	2,161	2,598
Other Liabilities
Long-term debt and capital leases	244	244
Nuclear decommissioning reserve	269	287
Nuclear decommissioning trust liability	415	339
Postretirement and other benefit obligations	118	113
Deferred income taxes	112	186
Derivative instruments	110	157
Out-of-market contracts, net	66	80
Non-current liabilities held-for-sale	0	0
Other non-current liabilities	295	283
Non-current liabilities - discontinued operations		0
Total non-current liabilities	1,629	1,689
Total Liabilities	3,790	4,287
Redeemable noncontrolling interest in subsidiaries	0	0
Total Stockholders' Equity	3,470	5,474
Total Liabilities and Stockholders' Equity	7,260	9,761
Non-Guarantor Subsidiaries
Current Assets
Cash and cash equivalents	348	615
Funds deposited by counterparties	0	0
Restricted cash	504	435
Accounts receivable - trade	306	321
Inventory	193	239
Derivative instruments	80	196
Cash collateral posted in support of energy risk management activities	1	34
Accounts receivable - affiliate	210	(254)
Current assets held-for-sale	107	9
Prepayments and other current assets	118	152
Current assets - discontinued operations		1,919
Total current assets	1,867	3,666
Net Property, Plant and Equipment	11,169	10,926
Other Assets
Investment in subsidiaries	28	145
Equity investments in affiliates	1,036	1,103
Notes receivable, less current portion	2	16
Goodwill	179	303
Intangible assets, net	1,291	1,384
Nuclear decommissioning trust fund	0	0
Deferred income taxes	(7)	0
Derivative instruments	40	44
Non-current assets held-for-sale	43	10
Other non-current assets	458	446
Non-current assets - discontinued operations		2,961
Total other assets	3,070	6,412
Total Assets	16,106	21,004
Current Liabilities
Current portion of long-term debt and capital leases	667	498
Accounts payable	280	247
Accounts payable - affiliate	(202)	(443)
Derivative instruments	108	237
Cash collateral received in support of energy risk management activities	0	0
Accrued interest expense	56	54
Current liabilities - held for sale	72
Other accrued expenses and other current liabilities	118	155
Other accrued expenses and other current liabilities - affiliate	0
Current liabilities - discontinued operations		1,210
Total current liabilities	1,099	1,958
Other Liabilities
Long-term debt and capital leases	8,733	8,252
Nuclear decommissioning reserve	0	0
Nuclear decommissioning trust liability	0	0
Postretirement and other benefit obligations	1	122
Deferred income taxes	64	125
Derivative instruments	107	170
Out-of-market contracts, net	141	150
Non-current liabilities held-for-sale	8	11
Other non-current liabilities	317	309
Non-current liabilities - discontinued operations		3,184
Total non-current liabilities	9,371	12,323
Total Liabilities	10,470	14,281
Redeemable noncontrolling interest in subsidiaries	78	46
Total Stockholders' Equity	5,558	6,677
Total Liabilities and Stockholders' Equity	16,106	21,004
NRG Energy, Inc.
Current Assets
Cash and cash equivalents	643	323
Funds deposited by counterparties	0	0
Restricted cash	0	0
Accounts receivable - trade	4	3
Inventory	0	0
Derivative instruments	9	1
Cash collateral posted in support of energy risk management activities	0	0
Accounts receivable - affiliate	(129)	200
Current assets held-for-sale	0	0
Prepayments and other current assets	27	62
Current assets - discontinued operations		0
Total current assets	554	589
Net Property, Plant and Equipment	238	251
Other Assets
Investment in subsidiaries	7,581	10,128
Equity investments in affiliates	2	30
Notes receivable, less current portion	36	(76)
Goodwill	0	0
Intangible assets, net	0	0
Nuclear decommissioning trust fund	0	0
Deferred income taxes	(236)	222
Derivative instruments	31	36
Non-current assets held-for-sale	0	0
Other non-current assets	120	328
Non-current assets - discontinued operations		0
Total other assets	7,534	10,668
Total Assets	8,326	11,508
Current Liabilities
Current portion of long-term debt and capital leases	57	(58)
Accounts payable	55	34
Accounts payable - affiliate	181	(200)
Derivative instruments	0	0
Cash collateral received in support of energy risk management activities	0	0
Accrued interest expense	97	123
Current liabilities - held for sale	0
Other accrued expenses and other current liabilities	328	342
Other accrued expenses and other current liabilities - affiliate	161
Current liabilities - discontinued operations		0
Total current liabilities	879	241
Other Liabilities
Long-term debt and capital leases	6,739	7,461
Nuclear decommissioning reserve	0	0
Nuclear decommissioning trust liability	0	0
Postretirement and other benefit obligations	339	275
Deferred income taxes	(155)	(291)
Derivative instruments	0	0
Out-of-market contracts, net	0	0
Non-current liabilities held-for-sale	0	0
Other non-current liabilities	52	74
Non-current liabilities - discontinued operations		0
Total non-current liabilities	6,975	7,519
Total Liabilities	7,854	7,760
Redeemable noncontrolling interest in subsidiaries	0	0
Total Stockholders' Equity	472	3,748
Total Liabilities and Stockholders' Equity	$ 8,326	$ 11,508

The amount of cash collateral received from hedge counterparties in support of energy risk management activities for which there is an offsetting liability within current liabilities. These amounts are segregated into separate accounts that are not contractually restricted but, based on the entity's intention, are not available for the payment of the entity's general corporate obligations. Depending on market fluctuations and the settlement of the underlying contracts, the entity will refund this collateral to the counterparties pursuant to the terms and conditions of the underlying trades.

No definition available.