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.

Condensed Consolidating Financial Information - CONSOLIDATING STATEMENTS OF CASH FLOWS (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Cash Flows from Operating Activities
Net income attributable to NRG Energy, Inc.	$ 313	$ 121	$ 201	$ 482	$ 434	$ 683
Net Income	313		202		434	684
Income from discontinued operations	0		13		0	401
Income from continuing operations	313		189		434	283
Adjustments to reconcile net income/(loss) to cash provided by operating activities:
Distributions from and equity in (earnings)/losses of unconsolidated affiliates					7	22
Depreciation and amortization					219	170
Accretion of asset retirement obligations					18	14
Provision for credit losses	24				48	52
Amortization of nuclear fuel					25	27
Amortization of financing costs and debt discount/premiums					12	13
Loss on debt extinguishment, net					1	47
Amortization of emissions allowances and energy credits					33	14
Amortization of unearned equity compensation					12	10
Net loss on sale of assets and disposal of assets					(15)	1
Impairment losses					18	1
Changes in derivative instruments					(131)	(22)
Changes in deferred income taxes and liability for uncertain tax benefits					116	(5)
Changes in collateral deposits in support of energy risk management activities					58	125
Changes in nuclear decommissioning trust liability					36	17
Changes in other working capital					(199)	(352)
Cash provided by continuing operations					692	417
Cash provided by discontinued operations					0	8
Net Cash Provided/(Used) by Operating Activities					692	425
Cash Flows from Investing Activities
Intercompany dividends					0	0
Payments for acquisitions of businesses					(5)	(21)
Capital expenditures					(116)	(107)
Net purchases of /proceeds from emission allowances					(4)	(1)
Investments in nuclear decommissioning trust fund securities					(257)	(209)
Proceeds from the sale of nuclear decommissioning trust fund securities					220	191
Proceeds from sale of assets, net of cash disposed and sale of discontinued operations, net of fees					15	1,289
Net distributions from investments in unconsolidated affiliates					2	7
Contributions to discontinued operations					0	(44)
Cash (used)/provided by continuing operations					(145)	1,105
Cash provided by (Used) discontinued operations					0	(2)
Net Cash (Used)/Provided by Investing Activities					(145)	1,103
Cash Flows from Financing Activities
Intercompany dividends and transfers					0	0
Payments of dividends to common stockholders					(148)	(16)
Payments for share repurchase activity					(229)	(1,075)
Payments for debt extinguishment costs					0	(24)
Purchase of and distributions to noncontrolling interests from subsidiaries					(2)	(1)
Proceeds from issuance of common stock					1	2
Proceeds from issuance of long-term debt					59	1,833
Payment of debt issuance costs					(1)	(33)
Repayments of long-term debt					(61)	(2,485)
Net repayment of Revolving Credit Facility					(83)	0
Other					(5)	0
Cash used by continuing operations					(469)	(1,799)
Cash provided by discontinued operations					0	43
Net Cash Used by Financing Activities					(469)	(1,756)
Effect of exchange rate changes on cash and cash equivalents					(1)	0
Change in Cash from discontinued operations					0	49
Net Increase/(Decrease) in Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash					77	(277)
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at Beginning of Period		385		613	385	613
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at End of Period	462		336		462	336
Eliminations
Cash Flows from Operating Activities
Net income attributable to NRG Energy, Inc.	(586)		(432)		(851)	(741)
Net Income	(586)		(432)		(851)	(741)
Income from discontinued operations			0			0
Income from continuing operations			(432)			(741)
Adjustments to reconcile net income/(loss) to cash provided by operating activities:
Distributions from and equity in (earnings)/losses of unconsolidated affiliates					851	741
Depreciation and amortization					0	0
Accretion of asset retirement obligations					0	0
Provision for credit losses					0	0
Amortization of nuclear fuel					0	0
Amortization of financing costs and debt discount/premiums					0	0
Loss on debt extinguishment, net					0	0
Amortization of emissions allowances and energy credits					0	0
Amortization of unearned equity compensation					0	0
Net loss on sale of assets and disposal of assets					0	0
Impairment losses					0	0
Changes in derivative instruments					0	0
Changes in deferred income taxes and liability for uncertain tax benefits					0	0
Changes in collateral deposits in support of energy risk management activities					0	0
Changes in nuclear decommissioning trust liability					0	0
Changes in other working capital					0	0
Cash provided by continuing operations						0
Cash provided by discontinued operations						0
Net Cash Provided/(Used) by Operating Activities					0	0
Cash Flows from Investing Activities
Intercompany dividends					(1,889)	(2,209)
Payments for acquisitions of businesses					0	0
Capital expenditures					0	0
Net purchases of /proceeds from 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 sale of assets, net of cash disposed and sale of discontinued operations, net of fees					0	0
Net distributions from investments in unconsolidated affiliates					0	0
Contributions to discontinued operations						0
Cash (used)/provided by continuing operations						(2,209)
Cash provided by (Used) discontinued operations						0
Net Cash (Used)/Provided by Investing Activities					(1,889)	(2,209)
Cash Flows from Financing Activities
Intercompany dividends and transfers					1,889	2,209
Payments of dividends to common stockholders					0	0
Payments for share repurchase activity					0	0
Payments for debt extinguishment costs						0
Purchase of and distributions to noncontrolling interests from subsidiaries					0	0
Proceeds from issuance of common stock					0	0
Proceeds from issuance of long-term debt					0	0
Payment of debt issuance costs					0	0
Repayments of long-term debt					0	0
Net repayment of Revolving Credit Facility					0
Other					0
Cash used by continuing operations						2,209
Cash provided by discontinued operations						0
Net Cash Used by Financing Activities					1,889	2,209
Effect of exchange rate changes on cash and cash equivalents					0
Change in Cash from discontinued operations						0
Net Increase/(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	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 attributable to NRG Energy, Inc.	573		389		842	644
Net Income	573		389		842	644
Income from discontinued operations			0			9
Income from continuing operations			389			635
Adjustments to reconcile net income/(loss) to cash provided by operating activities:
Distributions from and equity in (earnings)/losses of unconsolidated affiliates					(6)	(12)
Depreciation and amortization					160	104
Accretion of asset retirement obligations					10	11
Provision for credit losses					47	42
Amortization of nuclear fuel					25	27
Amortization of financing costs and debt discount/premiums					0	0
Loss on debt extinguishment, net					0	0
Amortization of emissions allowances and energy credits					24	13
Amortization of unearned equity compensation					0	0
Net loss on sale of assets and disposal of assets					(9)	(3)
Impairment losses					0	1
Changes in derivative instruments					(144)	(28)
Changes in deferred income taxes and liability for uncertain tax benefits					1,212	0
Changes in collateral deposits in support of energy risk management activities					53	128
Changes in nuclear decommissioning trust liability					36	17
Changes in other working capital					(124)	(343)
Cash provided by continuing operations						592
Cash provided by discontinued operations						17
Net Cash Provided/(Used) by Operating Activities					2,126	609
Cash Flows from Investing Activities
Intercompany dividends					0	0
Payments for acquisitions of businesses					(5)	(21)
Capital expenditures					(78)	(77)
Net purchases of /proceeds from emission allowances					(4)	(1)
Investments in nuclear decommissioning trust fund securities					(257)	(209)
Proceeds from the sale of nuclear decommissioning trust fund securities					220	191
Proceeds from sale of assets, net of cash disposed and sale of discontinued operations, net of fees					10	1
Net distributions from investments in unconsolidated affiliates					0	0
Contributions to discontinued operations						0
Cash (used)/provided by continuing operations						(116)
Cash provided by (Used) discontinued operations						0
Net Cash (Used)/Provided by Investing Activities					(114)	(116)
Cash Flows from Financing Activities
Intercompany dividends and transfers					(1,941)	(532)
Payments of dividends to common stockholders					0	0
Payments for share repurchase activity					0	0
Payments for debt extinguishment costs						0
Purchase of and distributions to noncontrolling interests from subsidiaries					0	0
Proceeds from issuance of common stock					0	0
Proceeds from issuance of long-term debt					0	0
Payment of debt issuance costs					0	0
Repayments of long-term debt					(60)	0
Net repayment of Revolving Credit Facility					0
Other					(5)
Cash used by continuing operations						(532)
Cash provided by discontinued operations						0
Net Cash Used by Financing Activities					(2,006)	(532)
Effect of exchange rate changes on cash and cash equivalents					0
Change in Cash from discontinued operations						17
Net Increase/(Decrease) in Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash					6	(56)
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at Beginning of Period		37		95	37	95
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at End of Period	43		39		43	39
Non-Guarantor Subsidiaries
Cash Flows from Operating Activities
Net income attributable to NRG Energy, Inc.	13		43		9	97
Net Income	13		44		9	98
Income from discontinued operations			0			5
Income from continuing operations			44			93
Adjustments to reconcile net income/(loss) to cash provided by operating activities:
Distributions from and equity in (earnings)/losses of unconsolidated affiliates					7	22
Depreciation and amortization					39	50
Accretion of asset retirement obligations					8	3
Provision for credit losses					1	4
Amortization of nuclear fuel					0	0
Amortization of financing costs and debt discount/premiums					0	0
Loss on debt extinguishment, net					0	0
Amortization of emissions allowances and energy credits					9	1
Amortization of unearned equity compensation					0	0
Net loss on sale of assets and disposal of assets					(1)	1
Impairment losses					18	0
Changes in derivative instruments					13	(32)
Changes in deferred income taxes and liability for uncertain tax benefits					(154)	(3)
Changes in collateral deposits in support of energy risk management activities					5	(3)
Changes in nuclear decommissioning trust liability					0	0
Changes in other working capital					(19)	(64)
Cash provided by continuing operations						72
Cash provided by discontinued operations						(9)
Net Cash Provided/(Used) by Operating Activities					(65)	63
Cash Flows from Investing Activities
Intercompany dividends					0	0
Payments for acquisitions of businesses					0	0
Capital expenditures					(20)	(15)
Net purchases of /proceeds from 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 sale of assets, net of cash disposed and sale of discontinued operations, net of fees					0	400
Net distributions from investments in unconsolidated affiliates					2	7
Contributions to discontinued operations						(44)
Cash (used)/provided by continuing operations						348
Cash provided by (Used) discontinued operations						(2)
Net Cash (Used)/Provided by Investing Activities					(18)	346
Cash Flows from Financing Activities
Intercompany dividends and transfers					86	(375)
Payments of dividends to common stockholders					0	0
Payments for share repurchase activity					0	0
Payments for debt extinguishment costs						0
Purchase of and distributions to noncontrolling interests from subsidiaries					(2)	(1)
Proceeds from issuance of common stock					0	0
Proceeds from issuance of long-term debt					0	0
Payment of debt issuance costs					0	0
Repayments of long-term debt					(1)	(53)
Net repayment of Revolving Credit Facility					0
Other					0
Cash used by continuing operations						(429)
Cash provided by discontinued operations						43
Net Cash Used by Financing Activities					83	(386)
Effect of exchange rate changes on cash and cash equivalents					(1)
Change in Cash from discontinued operations						32
Net Increase/(Decrease) in Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash					(1)	(9)
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at Beginning of Period		21		38	21	38
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at End of Period	20		29		20	29
NRG Energy, Inc. (Note Issuer)
Cash Flows from Operating Activities
Net income attributable to NRG Energy, Inc.	313		201		434	683
Net Income	313		201		434	683
Income from discontinued operations			13			387
Income from continuing operations			188			296
Adjustments to reconcile net income/(loss) to cash provided by operating activities:
Distributions from and equity in (earnings)/losses of unconsolidated affiliates					(845)	(729)
Depreciation and amortization					20	16
Accretion of asset retirement obligations					0	0
Provision for credit losses					0	6
Amortization of nuclear fuel					0	0
Amortization of financing costs and debt discount/premiums					12	13
Loss on debt extinguishment, net					1	47
Amortization of emissions allowances and energy credits					0	0
Amortization of unearned equity compensation					12	10
Net loss on sale of assets and disposal of assets					(5)	3
Impairment losses					0	0
Changes in derivative instruments					0	38
Changes in deferred income taxes and liability for uncertain tax benefits					(942)	(2)
Changes in collateral deposits in support of energy risk management activities					0	0
Changes in nuclear decommissioning trust liability					0	0
Changes in other working capital					(56)	55
Cash provided by continuing operations						(247)
Cash provided by discontinued operations						0
Net Cash Provided/(Used) by Operating Activities					(1,369)	(247)
Cash Flows from Investing Activities
Intercompany dividends					1,889	2,209
Payments for acquisitions of businesses					0	0
Capital expenditures					(18)	(15)
Net purchases of /proceeds from 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 sale of assets, net of cash disposed and sale of discontinued operations, net of fees					5	888
Net distributions from investments in unconsolidated affiliates					0	0
Contributions to discontinued operations						0
Cash (used)/provided by continuing operations						3,082
Cash provided by (Used) discontinued operations						0
Net Cash (Used)/Provided by Investing Activities					1,876	3,082
Cash Flows from Financing Activities
Intercompany dividends and transfers					(34)	(1,302)
Payments of dividends to common stockholders					(148)	(16)
Payments for share repurchase activity					(229)	(1,075)
Payments for debt extinguishment costs						(24)
Purchase of and distributions to noncontrolling interests from subsidiaries					0	0
Proceeds from issuance of common stock					1	2
Proceeds from issuance of long-term debt					59	1,833
Payment of debt issuance costs					(1)	(33)
Repayments of long-term debt					0	(2,432)
Net repayment of Revolving Credit Facility					(83)
Other					0
Cash used by continuing operations						(3,047)
Cash provided by discontinued operations						0
Net Cash Used by Financing Activities					(435)	(3,047)
Effect of exchange rate changes on cash and cash equivalents					0
Change in Cash from discontinued operations						0
Net Increase/(Decrease) in Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash					72	(212)
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at Beginning of Period		$ 327		$ 480	327	480
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at End of Period	$ 399		$ 268		$ 399	$ 268