Condensed Consolidating Financial Information - CASH FLOWS (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Cash Flows from Operating Activities
Net Income/(Loss)	$ 96	$ (642)	$ 329	$ (845)
Loss from discontinued operations	(25)	(741)	(25)	(775)
Net income	121	99	354	(70)
Adjustments to reconcile net income to net cash provided/(used) by operating activities:
Distributions from unconsolidated affiliates			43	28
Equity in (earnings)/losses of unconsolidated affiliates			(16)	(2)
Depreciation, amortization and accretion			485	517
Provision for bad debts			31	18
Amortization of nuclear fuel			24	24
Amortization of financing costs and debt discount/premiums			27	29
Adjustment for debt extinguishment			3	0
Amortization of intangibles and out-of-market contracts			48	51
Amortization of unearned equity compensation			26	16
Impairment losses			89	63
Changes in deferred income taxes and liability for uncertain tax benefits			4	8
Changes in nuclear decommissioning trust liability			41	2
Changes in derivative instruments			(211)	7
Changes in collateral deposits in support of energy risk management activities			(18)	(189)
Gain on sale of emission allowances			(11)	11
Gain on sale of assets			(16)	(22)
Loss on deconsolidation of business			22	0
Changes in other working capital			(401)	(379)
Cash provided by continuing operations			524	112
Cash used by discontinued operations			0	(38)
Net Cash Provided by Operating Activities			524	74
Cash Flows from Investing Activities
Dividends from NRG Yield, Inc.			0	0
Intercompany dividends				0
Acquisition of Drop Down Assets, net of cash acquired			0	0
Acquisitions of businesses, net of cash acquired			(284)	(16)
Capital expenditures			(691)	(542)
Decrease in notes receivable			4	8
Purchases of emission allowances			(22)	(30)
Proceeds from sale of emission allowances			34	59
Investments in nuclear decommissioning trust fund securities			(346)	(279)
Proceeds from the sale of nuclear decommissioning trust fund securities			303	277
Proceeds from renewable energy grants and state rebates			0	8
Proceeds from sale of assets, net of cash disposed of			18	35
Deconsolidation of business			(160)	0
Change in investments in unconsolidated affiliates			(2)	(30)
Other			0	18
Cash (used)/provided by continuing operations			(1,146)	(492)
Cash used by discontinued operations			0	(53)
Net Cash (Used)/Provided by Investing Activities			(1,146)	(545)
Cash Flows from Financing Activities
Dividends from NRG Yield, Inc.			0	0
Payment (for)/from intercompany loans			0	0
Acquisition of Drop Down Assets, net of cash acquired			0	0
Intercompany dividends				0
Payment of dividends to common and preferred stockholders			(19)	(19)
Payment for treasury stock			(500)	0
Net receipts from settlement of acquired derivatives that include financing elements			0	2
Proceeds from issuance of long-term debt			1,605	946
Payments for short and long-term debt			(848)	(530)
Increase in notes receivable from affiliate			0	(125)
Distributions to, net of contributions from, noncontrolling interests in subsidiaries			222	14
Payment of debt issuance costs			(37)	(36)
Other - contingent consideration			0	(10)
Cash provided by continuing operations			423	242
Cash used by discontinued operations			0	(224)
Net Cash Provided by Financing Activities			423	18
Effect of exchange rate changes on cash and cash equivalents			0	(8)
Change in Cash from discontinued operations			0	(315)
Net Decrease in Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash			(199)	(146)
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at Beginning of Period			1,536	1,386
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at End of Period	1,337	1,240	1,337	1,240
Eliminations
Cash Flows from Operating Activities
Net Income/(Loss)	(360)	106	(692)	53
Loss from discontinued operations	0	0	0	0
Net income	(360)	106	(692)	53
Adjustments to reconcile net income to net cash provided/(used) by operating activities:
Distributions from unconsolidated affiliates			(7)	(4)
Equity in (earnings)/losses of unconsolidated affiliates			0	0
Depreciation, amortization and accretion			0	0
Provision for bad debts			0	0
Amortization of nuclear fuel			0	0
Amortization of financing costs and debt discount/premiums			0	0
Adjustment for debt extinguishment			0
Amortization of intangibles and out-of-market contracts			0	0
Amortization of unearned equity compensation			0	0
Impairment losses			0	0
Changes in deferred income taxes and liability for uncertain tax benefits			0	0
Changes in nuclear decommissioning trust liability			0	0
Changes in derivative instruments			(22)	0
Changes in collateral deposits in support of energy risk management activities			0	0
Gain on sale of emission allowances			0	0
Gain on sale of assets			0	0
Loss on deconsolidation of business			0
Changes in other working capital			721	(49)
Cash provided by continuing operations				0
Cash used by discontinued operations				0
Net Cash Provided by Operating Activities			0	0
Cash Flows from Investing Activities
Dividends from NRG Yield, Inc.			(52)	(45)
Intercompany dividends				(129)
Acquisition of Drop Down Assets, net of cash acquired			126	131
Acquisitions of businesses, net of cash acquired			0	0
Capital expenditures			0	0
Decrease in notes receivable			0	0
Purchases of emission allowances			0	0
Proceeds from sale of emission allowances			0	0
Investments in nuclear decommissioning trust fund securities			0	0
Proceeds from the sale of nuclear decommissioning trust fund securities			0	0
Proceeds from renewable energy grants and state rebates				0
Proceeds from sale of assets, net of cash disposed of			0	0
Deconsolidation of business			0
Change in investments in unconsolidated affiliates			0	0
Other				0
Cash (used)/provided by continuing operations				(43)
Cash used by discontinued operations				0
Net Cash (Used)/Provided by Investing Activities			74	(43)
Cash Flows from Financing Activities
Dividends from NRG Yield, Inc.			52	45
Payment (for)/from intercompany loans			0	129
Acquisition of Drop Down Assets, net of cash acquired			(126)	(131)
Intercompany dividends				0
Payment of dividends to common and preferred stockholders			0	0
Payment for treasury stock			0
Net receipts from settlement of acquired derivatives that include financing elements				0
Proceeds from issuance of long-term debt			0	0
Payments for short and long-term debt			0	0
Increase in notes receivable from affiliate				0
Distributions to, net of contributions from, noncontrolling interests in subsidiaries			0	0
Payment of debt issuance costs			0	0
Other - contingent consideration				0
Cash provided by continuing operations				43
Cash used by discontinued operations				0
Net Cash Provided by Financing Activities			(74)	43
Effect of exchange rate changes on cash and cash equivalents				0
Change in Cash from discontinued operations				0
Net Decrease in Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash			0	0
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at Beginning of Period			0	0
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at End of Period	0	0	0	0
Guarantor Subsidiaries
Cash Flows from Operating Activities
Net Income/(Loss)	210	186	543	263
Loss from discontinued operations	0	0	0	0
Net income	210	186	543	263
Adjustments to reconcile net income to net cash provided/(used) by operating activities:
Distributions from unconsolidated affiliates			0	0
Equity in (earnings)/losses of unconsolidated affiliates			0	0
Depreciation, amortization and accretion			162	198
Provision for bad debts			31	17
Amortization of nuclear fuel			24	24
Amortization of financing costs and debt discount/premiums			0	0
Adjustment for debt extinguishment			0
Amortization of intangibles and out-of-market contracts			9	12
Amortization of unearned equity compensation			0	0
Impairment losses			0	42
Changes in deferred income taxes and liability for uncertain tax benefits			221	131
Changes in nuclear decommissioning trust liability			41	2
Changes in derivative instruments			(154)	12
Changes in collateral deposits in support of energy risk management activities			(4)	(203)
Gain on sale of emission allowances			(11)	11
Gain on sale of assets			(3)	(22)
Loss on deconsolidation of business			0
Changes in other working capital			(298)	(329)
Cash provided by continuing operations				158
Cash used by discontinued operations				0
Net Cash Provided by Operating Activities			561	158
Cash Flows from Investing Activities
Dividends from NRG Yield, Inc.			0	0
Intercompany dividends				0
Acquisition of Drop Down Assets, net of cash acquired			0	0
Acquisitions of businesses, net of cash acquired			(2)	0
Capital expenditures			(105)	(90)
Decrease in notes receivable			0	8
Purchases of emission allowances			(22)	(30)
Proceeds from sale of emission allowances			34	59
Investments in nuclear decommissioning trust fund securities			(346)	(279)
Proceeds from the sale of nuclear decommissioning trust fund securities			303	277
Proceeds from renewable energy grants and state rebates				0
Proceeds from sale of assets, net of cash disposed of			10	35
Deconsolidation of business			0
Change in investments in unconsolidated affiliates			0	0
Other				18
Cash (used)/provided by continuing operations				(2)
Cash used by discontinued operations				0
Net Cash (Used)/Provided by Investing Activities			(128)	(2)
Cash Flows from Financing Activities
Dividends from NRG Yield, Inc.			0	0
Payment (for)/from intercompany loans			(323)	0
Acquisition of Drop Down Assets, net of cash acquired			0	0
Intercompany dividends				(122)
Payment of dividends to common and preferred stockholders			0	0
Payment for treasury stock			0
Net receipts from settlement of acquired derivatives that include financing elements				0
Proceeds from issuance of long-term debt			0	0
Payments for short and long-term debt			0	0
Increase in notes receivable from affiliate				0
Distributions to, net of contributions from, noncontrolling interests in subsidiaries			0	0
Payment of debt issuance costs			0	0
Other - contingent consideration				0
Cash provided by continuing operations				(122)
Cash used by discontinued operations				0
Net Cash Provided by Financing Activities			(323)	(122)
Effect of exchange rate changes on cash and cash equivalents				0
Change in Cash from discontinued operations				0
Net Decrease in Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash			110	34
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at Beginning of Period			41	13
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at End of Period	151	47	151	47
Non-Guarantor Subsidiaries
Cash Flows from Operating Activities
Net Income/(Loss)	95	(336)	32	(396)
Loss from discontinued operations	0	(123)	0	(160)
Net income	95	(213)	32	(236)
Adjustments to reconcile net income to net cash provided/(used) by operating activities:
Distributions from unconsolidated affiliates			50	32
Equity in (earnings)/losses of unconsolidated affiliates			(17)	(4)
Depreciation, amortization and accretion			307	303
Provision for bad debts			0	1
Amortization of nuclear fuel			0	0
Amortization of financing costs and debt discount/premiums			18	20
Adjustment for debt extinguishment			0
Amortization of intangibles and out-of-market contracts			39	39
Amortization of unearned equity compensation			0	0
Impairment losses			89	21
Changes in deferred income taxes and liability for uncertain tax benefits			(41)	237
Changes in nuclear decommissioning trust liability			0	0
Changes in derivative instruments			(43)	(12)
Changes in collateral deposits in support of energy risk management activities			(14)	11
Gain on sale of emission allowances			0	0
Gain on sale of assets			(13)	0
Loss on deconsolidation of business			22
Changes in other working capital			41	(539)
Cash provided by continuing operations				(127)
Cash used by discontinued operations				(38)
Net Cash Provided by Operating Activities			470	(165)
Cash Flows from Investing Activities
Dividends from NRG Yield, Inc.			0	0
Intercompany dividends				0
Acquisition of Drop Down Assets, net of cash acquired			(126)	(131)
Acquisitions of businesses, net of cash acquired			(282)	(16)
Capital expenditures			(556)	(436)
Decrease in notes receivable			4	0
Purchases of emission allowances			0	0
Proceeds from sale of emission allowances			0	0
Investments in nuclear decommissioning trust fund securities			0	0
Proceeds from the sale of nuclear decommissioning trust fund securities			0	0
Proceeds from renewable energy grants and state rebates				8
Proceeds from sale of assets, net of cash disposed of			8	0
Deconsolidation of business			(160)
Change in investments in unconsolidated affiliates			(2)	(30)
Other				0
Cash (used)/provided by continuing operations				(605)
Cash used by discontinued operations				(53)
Net Cash (Used)/Provided by Investing Activities			(1,114)	(658)
Cash Flows from Financing Activities
Dividends from NRG Yield, Inc.			(52)	(45)
Payment (for)/from intercompany loans			108	(129)
Acquisition of Drop Down Assets, net of cash acquired			0	0
Intercompany dividends				369
Payment of dividends to common and preferred stockholders			0	0
Payment for treasury stock			0
Net receipts from settlement of acquired derivatives that include financing elements				2
Proceeds from issuance of long-term debt			774	741
Payments for short and long-term debt			(564)	(316)
Increase in notes receivable from affiliate				(125)
Distributions to, net of contributions from, noncontrolling interests in subsidiaries			222	14
Payment of debt issuance costs			(24)	(32)
Other - contingent consideration				(10)
Cash provided by continuing operations				469
Cash used by discontinued operations				(224)
Net Cash Provided by Financing Activities			464	245
Effect of exchange rate changes on cash and cash equivalents				(8)
Change in Cash from discontinued operations				(315)
Net Decrease in Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash			(180)	(271)
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at Beginning of Period			852	1,050
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at End of Period	672	779	672	779
NRG Energy, Inc. (Note Issuer)
Cash Flows from Operating Activities
Net Income/(Loss)	151	(598)	446	(765)
Loss from discontinued operations	(25)	(618)	(25)	(615)
Net income	176	20	471	(150)
Adjustments to reconcile net income to net cash provided/(used) by operating activities:
Distributions from unconsolidated affiliates			0	0
Equity in (earnings)/losses of unconsolidated affiliates			1	2
Depreciation, amortization and accretion			16	16
Provision for bad debts			0	0
Amortization of nuclear fuel			0	0
Amortization of financing costs and debt discount/premiums			9	9
Adjustment for debt extinguishment			3
Amortization of intangibles and out-of-market contracts			0	0
Amortization of unearned equity compensation			26	16
Impairment losses			0	0
Changes in deferred income taxes and liability for uncertain tax benefits			(176)	(360)
Changes in nuclear decommissioning trust liability			0	0
Changes in derivative instruments			8	7
Changes in collateral deposits in support of energy risk management activities			0	3
Gain on sale of emission allowances			0	0
Gain on sale of assets			0	0
Loss on deconsolidation of business			0
Changes in other working capital			(865)	538
Cash provided by continuing operations				81
Cash used by discontinued operations				0
Net Cash Provided by Operating Activities			(507)	81
Cash Flows from Investing Activities
Dividends from NRG Yield, Inc.			52	45
Intercompany dividends				129
Acquisition of Drop Down Assets, net of cash acquired			0	0
Acquisitions of businesses, net of cash acquired			0	0
Capital expenditures			(30)	(16)
Decrease in notes receivable			0	0
Purchases of emission allowances			0	0
Proceeds from sale of emission allowances			0	0
Investments in nuclear decommissioning trust fund securities			0	0
Proceeds from the sale of nuclear decommissioning trust fund securities			0	0
Proceeds from renewable energy grants and state rebates				0
Proceeds from sale of assets, net of cash disposed of			0	0
Deconsolidation of business			0
Change in investments in unconsolidated affiliates			0	0
Other				0
Cash (used)/provided by continuing operations				158
Cash used by discontinued operations				0
Net Cash (Used)/Provided by Investing Activities			22	158
Cash Flows from Financing Activities
Dividends from NRG Yield, Inc.			0	0
Payment (for)/from intercompany loans			215	0
Acquisition of Drop Down Assets, net of cash acquired			126	131
Intercompany dividends				(247)
Payment of dividends to common and preferred stockholders			(19)	(19)
Payment for treasury stock			(500)
Net receipts from settlement of acquired derivatives that include financing elements				0
Proceeds from issuance of long-term debt			831	205
Payments for short and long-term debt			(284)	(214)
Increase in notes receivable from affiliate				0
Distributions to, net of contributions from, noncontrolling interests in subsidiaries			0	0
Payment of debt issuance costs			(13)	(4)
Other - contingent consideration				0
Cash provided by continuing operations				(148)
Cash used by discontinued operations				0
Net Cash Provided by Financing Activities			356	(148)
Effect of exchange rate changes on cash and cash equivalents				0
Change in Cash from discontinued operations				0
Net Decrease in Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash			(129)	91
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at Beginning of Period			643	323
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at End of Period	$ 514	$ 414	$ 514	$ 414

The aggregate (income) expense recorded in earnings to allocate the cost of out-of-market contracts and intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash (income) expense, this element is added back to net income when calculating cash provided by (used in) operations using the indirect method.

No definition available.