Condensed Consolidating Financial Information (Statements of Cash Flows) (Details 5) - USD ($) $ in Millions		3 Months Ended												12 Months Ended
		Dec. 31, 2016		Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016		Dec. 31, 2015		Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015		Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Cash Flows from Operating Activities
Net (Loss)/Income		$ (1,055)		$ 393	$ (276)	$ 47		$ (6,358)		$ 67	$ (9)	$ (136)		$ (891)		$ (6,436)		$ 132
Adjustments to reconcile net income to net cash provided/(used) by operating activities:
Proceeds from Equity Method Investment, Dividends or Distributions														81		73		87
Equity in earnings of unconsolidated affiliates														(27)		(36)		(38)
Depreciation and amortization														1,367		1,566		1,523
Provision for bad debts														48		64		64
Amortization of nuclear fuel														49		45		46
Amortization of Financing Costs and Discounts														3		(11)		(12)
Gains Losses on Extinguishment of Debt, Non Cash Portion														21		(75)		25
Amortization of Intangibles and Out of Market Contracts														91		81		64
Share-based Compensation														10		41		42
Net (gain)/loss on sale of assets and equity method investments														(224)		14		(4)
Changes in nuclear decommissioning trust liability														(41)		2		(19)
Increase (Decrease) in Other Operating Assets and Liabilities, Net														92		149		217
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments														0		(21)		0
Impairment Charges and Asset Write Downs														1,186		5,086		97
Changes in Derivatives														23		233		(61)
Changes in Collateral Deposits Supporting Energy Risk Management Activities														365		(381)		146
Gain on sale of emissions allowances														47		0		0
Increase (Decrease) in Income Taxes														(43)		1,326		(154)
Other assets and liabilities														(75)		(258)		(466)
Net Cash Provided by Operating Activities														2,072		1,309		1,510
Cash Flows from Investing Activities
Payments to Acquire Business Two, Net of Cash Acquired														0		0
Intercompany Dividend Proceeds - Investing														0		0
Acquisition of businesses, net of cash acquired														(209)		(31)		(2,936)
Capital expenditures														(1,244)		(1,283)		(909)
(Increase)/decrease in restricted cash, net														(29)		8		57
Increase Decrease in Restricted Cash to Support Equity Requirements for U.S. DOE Funded Projects														(3)		35		(206)
Increase (Decrease) in Notes Receivables														17		18		25
Proceeds from Renewable Energy Grants														(36)		(82)		(916)
Purchases of emission allowances, net of proceeds														(1)		41		(16)
Payments to Acquire Available-for-sale Securities														(551)		(629)		(619)
Proceeds from sales of nuclear decommissioning trust fund securities														510		631		600
Proceeds/(purchases) from sale of assets, net														636		27		203
(Investments in)/proceeds from sales of unconsolidated affiliates, net														34		395		103
Other														48		11		85
Net Cash Used by Investing Activities														(824)		(1,485)		(2,903)
Cash Flows from Financing Activities
(Payments)/proceeds from intercompany loans														0		0		0
Payments to Acquire Business Three, Net of Cash Acquired														0		0
Intercompany Dividend Proceeds - Financing														0		0
Payments of Ordinary Dividends, Common Stock														(76)		(201)		(196)
Net receipts from/(payments for) settlement of acquired derivatives that include financing elements														151		196		9
Payments for Repurchase of Redeemable Preferred Stock					$ (226)									(226)		0		0
Proceeds from (Payments to) Noncontrolling Interests														(156)		47		189
Proceeds from sale of noncontrolling interests in subsidiaries														0		600		630
Payments for treasury stock														0		(437)		(39)
Proceeds from issuance of common stock, net of issuance costs														(1)		(1)		(21)
Proceeds from issuance of long-term debt														(5,527)		(1,004)		(4,563)
Payments of debt issuance and hedging costs														(89)		(21)		(67)
Payments for short and long-term debt														5,913		1,599		3,827
Proceeds from (Payments for) Other Financing Activities														(13)		(22)		(18)
Net Cash Provided by Financing Activities														(794)		(432)		1,265
Effect of exchange rate changes on cash and cash equivalents														1		10		(10)
Net Increase/(Decrease) in Cash and Cash Equivalents														455		(598)		(138)
Cash and Cash Equivalents at Beginning of Period						1,518						2,116		1,518		2,116		2,254
Cash and Cash Equivalents at End of Period		1,973						1,518						1,973		1,518		2,116
Guarantor Subsidiaries
Cash Flows from Operating Activities
Net (Loss)/Income														596		(2,586)		924
Adjustments to reconcile net income to net cash provided/(used) by operating activities:
Proceeds from Equity Method Investment, Dividends or Distributions														0		3		0
Equity in earnings of unconsolidated affiliates														(5)		(8)		(13)
Depreciation and amortization														565		787		801
Provision for bad debts														41		58		64
Amortization of nuclear fuel														49		45		46
Amortization of Financing Costs and Discounts														0		0		0
Gains Losses on Extinguishment of Debt, Non Cash Portion														0		0		0
Amortization of Intangibles and Out of Market Contracts														39		52		65
Share-based Compensation														0		0		0
Net (gain)/loss on sale of assets and equity method investments														0		0		0
Changes in nuclear decommissioning trust liability														(41)		2		(19)
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments																0
Impairment Charges and Asset Write Downs														378		4,655		0
Changes in Derivatives														(77)		264		(149)
Changes in Collateral Deposits Supporting Energy Risk Management Activities														437		(360)		101
Gain on sale of emissions allowances														47
Increase (Decrease) in Income Taxes														(1)		(1,092)		242
Other assets and liabilities														(1,806)		(8,744)		686
Net Cash Provided by Operating Activities														304		(6,928)		2,786
Cash Flows from Investing Activities
Payments to Acquire Business Two, Net of Cash Acquired														0		0
Intercompany Dividend Proceeds - Investing														0		0
Acquisition of businesses, net of cash acquired														0		0		0
Capital expenditures														(180)		(316)		(252)
(Increase)/decrease in restricted cash, net														(4)		(1)		0
Increase Decrease in Restricted Cash to Support Equity Requirements for U.S. DOE Funded Projects														0		0		0
Increase (Decrease) in Notes Receivables														0		0		0
Proceeds from Renewable Energy Grants														0		0		0
Purchases of emission allowances, net of proceeds														(1)		41		(16)
Payments to Acquire Available-for-sale Securities														(551)		(629)		(619)
Proceeds from sales of nuclear decommissioning trust fund securities														510		631		600
Proceeds/(purchases) from sale of assets, net														0		0		0
(Investments in)/proceeds from sales of unconsolidated affiliates, net														(3)		(1)		0
Other														27		0		0
Net Cash Used by Investing Activities														(196)		(273)		(287)
Cash Flows from Financing Activities
(Payments)/proceeds from intercompany loans														52		(7,183)		2,523
Payments to Acquire Business Three, Net of Cash Acquired														0		0
Intercompany Dividend Proceeds - Financing														(52)		0
Payments of Ordinary Dividends, Common Stock														0		0		0
Net receipts from/(payments for) settlement of acquired derivatives that include financing elements														0		0		0
Payments for Repurchase of Redeemable Preferred Stock														0
Proceeds from (Payments to) Noncontrolling Interests														0		0		0
Proceeds from sale of noncontrolling interests in subsidiaries																0		0
Payments for treasury stock																0		0
Proceeds from issuance of common stock, net of issuance costs														0		0		0
Proceeds from issuance of long-term debt														0		0		0
Payments of debt issuance and hedging costs														0		0		0
Payments for short and long-term debt														1		0		0
Proceeds from (Payments for) Other Financing Activities														(3)		0		(14)
Net Cash Provided by Financing Activities														(108)		7,183		(2,537)
Effect of exchange rate changes on cash and cash equivalents														0		0		0
Net Increase/(Decrease) in Cash and Cash Equivalents														0		(18)		(38)
Cash and Cash Equivalents at Beginning of Period						0						18		0		18		56
Cash and Cash Equivalents at End of Period		0						0						0		0		18
Non-Guarantor Subsidiaries
Cash Flows from Operating Activities
Net (Loss)/Income														(592)		(351)		426
Adjustments to reconcile net income to net cash provided/(used) by operating activities:
Proceeds from Equity Method Investment, Dividends or Distributions														89		91		87
Equity in earnings of unconsolidated affiliates														(37)		(37)		(33)
Depreciation and amortization														776		759		706
Provision for bad debts														7		3		0
Amortization of nuclear fuel														0		0		0
Amortization of Financing Costs and Discounts														(18)		(37)		(40)
Gains Losses on Extinguishment of Debt, Non Cash Portion														4		(56)		8
Amortization of Intangibles and Out of Market Contracts														52		29		(1)
Share-based Compensation														0		0		0
Net (gain)/loss on sale of assets and equity method investments														(294)		0		(4)
Changes in nuclear decommissioning trust liability														0		0		0
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments																(21)
Impairment Charges and Asset Write Downs														808		400		119
Changes in Derivatives														136		(31)		88
Changes in Collateral Deposits Supporting Energy Risk Management Activities														(72)		(21)		45
Gain on sale of emissions allowances														0
Increase (Decrease) in Income Taxes														18		(237)		(115)
Other assets and liabilities														364		(847)		(958)
Net Cash Provided by Operating Activities														1,241		(356)		328
Cash Flows from Investing Activities
Payments to Acquire Business Two, Net of Cash Acquired														(77)		(698)
Intercompany Dividend Proceeds - Investing														0		0
Acquisition of businesses, net of cash acquired														(209)		(31)		(25)
Capital expenditures														(1,016)		(908)		(619)
(Increase)/decrease in restricted cash, net														(25)		9		57
Increase Decrease in Restricted Cash to Support Equity Requirements for U.S. DOE Funded Projects														(3)		34		(209)
Increase (Decrease) in Notes Receivables														17		18		25
Proceeds from Renewable Energy Grants														(36)		(82)		(916)
Purchases of emission allowances, net of proceeds														0		0		0
Payments to Acquire Available-for-sale Securities														0		0		0
Proceeds from sales of nuclear decommissioning trust fund securities														0		0		0
Proceeds/(purchases) from sale of assets, net														619		1		0
(Investments in)/proceeds from sales of unconsolidated affiliates, net														37		357		25
Other														13		11		85
Net Cash Used by Investing Activities														(682)		(1,839)		205
Cash Flows from Financing Activities
(Payments)/proceeds from intercompany loans														49		(1,258)		685
Payments to Acquire Business Three, Net of Cash Acquired														0		0
Intercompany Dividend Proceeds - Financing														40		(33)
Payments of Ordinary Dividends, Common Stock														0		0		0
Net receipts from/(payments for) settlement of acquired derivatives that include financing elements														151		196		9
Payments for Repurchase of Redeemable Preferred Stock														0
Proceeds from (Payments to) Noncontrolling Interests														(156)		47		189
Proceeds from sale of noncontrolling interests in subsidiaries																600		630
Payments for treasury stock																0		0
Proceeds from issuance of common stock, net of issuance costs														0		0		0
Proceeds from issuance of long-term debt														(1,387)		(953)		(1,182)
Payments of debt issuance and hedging costs														(29)		(21)		(39)
Payments for short and long-term debt														988		1,353		1,160
Proceeds from (Payments for) Other Financing Activities														(10)		(22)		(4)
Net Cash Provided by Financing Activities														265		1,555		62
Effect of exchange rate changes on cash and cash equivalents														1		10		(10)
Net Increase/(Decrease) in Cash and Cash Equivalents														825		(630)		585
Cash and Cash Equivalents at Beginning of Period						825						1,455		825		1,455		870
Cash and Cash Equivalents at End of Period		1,650						825						1,650		825		1,455
NRG Energy, Inc.
Cash Flows from Operating Activities
Net (Loss)/Income														(718)		(6,351)		149
Adjustments to reconcile net income to net cash provided/(used) by operating activities:
Proceeds from Equity Method Investment, Dividends or Distributions														0		0		0
Equity in earnings of unconsolidated affiliates														5		0		0
Depreciation and amortization														26		20		16
Provision for bad debts														0		3		0
Amortization of nuclear fuel														0		0		0
Amortization of Financing Costs and Discounts														21		26		28
Gains Losses on Extinguishment of Debt, Non Cash Portion														17		(19)		17
Amortization of Intangibles and Out of Market Contracts														0		0		0
Share-based Compensation														10		41		42
Net (gain)/loss on sale of assets and equity method investments														70		14		0
Changes in nuclear decommissioning trust liability														0		0		0
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments																0
Impairment Charges and Asset Write Downs														0		31		0
Changes in Derivatives														(36)		0		0
Changes in Collateral Deposits Supporting Energy Risk Management Activities														0		0		0
Gain on sale of emissions allowances														0
Increase (Decrease) in Income Taxes														(60)		2,655		(281)
Other assets and liabilities														1,192		12,173		(1,575)
Net Cash Provided by Operating Activities														527		8,593		(1,604)
Cash Flows from Investing Activities
Payments to Acquire Business Two, Net of Cash Acquired														0		0
Intercompany Dividend Proceeds - Investing														(12)		(33)
Acquisition of businesses, net of cash acquired														0		0		(2,911)
Capital expenditures														(48)		(59)		(38)
(Increase)/decrease in restricted cash, net														0		0		0
Increase Decrease in Restricted Cash to Support Equity Requirements for U.S. DOE Funded Projects														0		1		3
Increase (Decrease) in Notes Receivables														0		0		0
Proceeds from Renewable Energy Grants														0		0		0
Purchases of emission allowances, net of proceeds														0		0		0
Payments to Acquire Available-for-sale Securities														0		0		0
Proceeds from sales of nuclear decommissioning trust fund securities														0		0		0
Proceeds/(purchases) from sale of assets, net														17		26		203
(Investments in)/proceeds from sales of unconsolidated affiliates, net														0		39		78
Other														8		0		0
Net Cash Used by Investing Activities														70		32		(2,761)
Cash Flows from Financing Activities
(Payments)/proceeds from intercompany loans														(101)		8,441		(3,208)
Payments to Acquire Business Three, Net of Cash Acquired														77		698
Intercompany Dividend Proceeds - Financing														0		0
Payments of Ordinary Dividends, Common Stock														(76)		(201)		(196)
Net receipts from/(payments for) settlement of acquired derivatives that include financing elements														0		0		0
Payments for Repurchase of Redeemable Preferred Stock														(226)
Proceeds from (Payments to) Noncontrolling Interests														0		0		0
Proceeds from sale of noncontrolling interests in subsidiaries																0		0
Payments for treasury stock																(437)		(39)
Proceeds from issuance of common stock, net of issuance costs														(1)		(1)		(21)
Proceeds from issuance of long-term debt														(4,140)		(51)		(3,381)
Payments of debt issuance and hedging costs														(60)		0		(28)
Payments for short and long-term debt														4,924		246		2,667
Proceeds from (Payments for) Other Financing Activities														0		0		0
Net Cash Provided by Financing Activities														(967)		(8,575)		3,680
Effect of exchange rate changes on cash and cash equivalents														0		0		0
Net Increase/(Decrease) in Cash and Cash Equivalents														(370)		50		(685)
Cash and Cash Equivalents at Beginning of Period						693						643		693		643		1,328
Cash and Cash Equivalents at End of Period		323						693						323		693		643
NRG Yield [Member]
Cash Flows from Financing Activities
Proceeds from issuance of common stock, net of issuance costs																		0
Consolidation, Eliminations [Member]
Cash Flows from Operating Activities
Net (Loss)/Income														(177)	[1],[2]	2,852	[3],[4]	(1,367)	[5],[6]
Adjustments to reconcile net income to net cash provided/(used) by operating activities:
Proceeds from Equity Method Investment, Dividends or Distributions														(8)	[2]	(21)	[4]	0	[6]
Equity in earnings of unconsolidated affiliates														10	[1],[2]	9	[3],[4]	8	[5],[6]
Depreciation and amortization														0	[1],[2]	0	[3],[4]	0	[5],[6]
Provision for bad debts														0	[2]	0	[4]	0	[6]
Amortization of nuclear fuel														0	[2]	0	[4]	0	[6]
Amortization of Financing Costs and Discounts														0	[2]	0	[4]	0	[6]
Gains Losses on Extinguishment of Debt, Non Cash Portion														0	[2]	0	[4]	0	[6]
Amortization of Intangibles and Out of Market Contracts														0	[2]	0	[4]	0	[6]
Share-based Compensation														0	[2]	0	[4]	0	[6]
Net (gain)/loss on sale of assets and equity method investments														0	[2]	0	[4]	0	[6]
Changes in nuclear decommissioning trust liability														0	[2]	0	[4]	0	[6]
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments	[3],[4]															0
Impairment Charges and Asset Write Downs														0	[2]	0	[4]	(22)	[6]
Changes in Derivatives														0	[2]	0	[4]	0	[6]
Changes in Collateral Deposits Supporting Energy Risk Management Activities														0	[2]	0	[4]	0	[6]
Gain on sale of emissions allowances	[2]													0
Increase (Decrease) in Income Taxes														0	[2]	0	[4]	0	[6]
Other assets and liabilities														175	[2]	(2,840)	[4]	1,381	[6]
Net Cash Provided by Operating Activities														0	[2]	0	[4]	0	[6]
Cash Flows from Investing Activities
Payments to Acquire Business Two, Net of Cash Acquired														77	[2]	698	[4]
Intercompany Dividend Proceeds - Investing														12	[2]	33	[4]
Acquisition of businesses, net of cash acquired														0	[2]	0	[4]	0	[6]
Capital expenditures														0	[2]	0	[4]	0	[6]
(Increase)/decrease in restricted cash, net														0	[2]	0	[4]	0	[6]
Increase Decrease in Restricted Cash to Support Equity Requirements for U.S. DOE Funded Projects														0	[2]	0	[4]	0	[6]
Increase (Decrease) in Notes Receivables														0	[2]	0	[4]	0	[6]
Proceeds from Renewable Energy Grants														0	[2]	0	[4]	0	[6]
Purchases of emission allowances, net of proceeds														0	[2]	0	[4]	0	[6]
Payments to Acquire Available-for-sale Securities														0	[2]	0	[4]	0	[6]
Proceeds from sales of nuclear decommissioning trust fund securities														0	[2]	0	[4]	0	[6]
Proceeds/(purchases) from sale of assets, net														0	[2]	0	[4]	0	[6]
(Investments in)/proceeds from sales of unconsolidated affiliates, net														0	[2]	0	[4]	0	[6]
Other														0	[2]	0	[4]	0	[6]
Net Cash Used by Investing Activities														(16)	[2]	595	[4]	(60)	[6]
Cash Flows from Financing Activities
(Payments)/proceeds from intercompany loans														0	[2]	0	[4]		[6]
Payments to Acquire Business Three, Net of Cash Acquired														(77)	[2]	(698)	[4]
Intercompany Dividend Proceeds - Financing														12	[2]	33	[4]
Payments of Ordinary Dividends, Common Stock														0	[2]	0	[4]	0	[6]
Net receipts from/(payments for) settlement of acquired derivatives that include financing elements														0	[2]	0	[4]	0	[6]
Payments for Repurchase of Redeemable Preferred Stock	[2]													0
Proceeds from (Payments to) Noncontrolling Interests														0	[2]	0	[4]	0	[6]
Proceeds from sale of noncontrolling interests in subsidiaries																0	[4]	0	[6]
Payments for treasury stock																0	[4]	0	[6]
Proceeds from issuance of common stock, net of issuance costs														0	[2]	0	[4]	0	[6]
Proceeds from issuance of long-term debt														0	[2]	0	[4]	0	[6]
Payments of debt issuance and hedging costs														0	[2]	0	[4]	0	[6]
Payments for short and long-term debt														0	[2]	0	[4]	0	[6]
Proceeds from (Payments for) Other Financing Activities														0	[2]	0	[4]	0	[6]
Net Cash Provided by Financing Activities														16	[2]	(595)	[4]	60	[6]
Effect of exchange rate changes on cash and cash equivalents														0	[2]	0	[4]	0	[6]
Net Increase/(Decrease) in Cash and Cash Equivalents														0	[2]	0	[4]	0	[6]
Cash and Cash Equivalents at Beginning of Period						$ 0	[2],[4],[7]					$ 0	[4],[6]	0	[2],[4],[7]	0	[4],[6]	0	[6]
Cash and Cash Equivalents at End of Period		$ 0	[2],[8]					$ 0	[2],[4],[7]					0	[2],[8]	0	[2],[4],[7]	0	[4],[6]
NRG Yield, Inc. [Member]
Cash Flows from Investing Activities
Intercompany Dividend Proceeds - Investing														0		0		0
Cash Flows from Financing Activities
Intercompany Dividend Proceeds - Financing														0		0		0
NRG Yield, Inc. [Member] | Guarantor Subsidiaries
Cash Flows from Investing Activities
Intercompany Dividend Proceeds - Investing														0		0		0
Cash Flows from Financing Activities
Intercompany Dividend Proceeds - Financing														0		0		0
NRG Yield, Inc. [Member] | Non-Guarantor Subsidiaries
Cash Flows from Investing Activities
Intercompany Dividend Proceeds - Investing														0		0		0
Cash Flows from Financing Activities
Intercompany Dividend Proceeds - Financing														(81)		(70)		(60)
NRG Yield, Inc. [Member] | NRG Energy, Inc.
Cash Flows from Investing Activities
Intercompany Dividend Proceeds - Investing														(81)		(70)		60
Cash Flows from Financing Activities
Intercompany Dividend Proceeds - Financing														0		0		0
NRG Yield, Inc. [Member] | Consolidation, Eliminations [Member]
Cash Flows from Investing Activities
Intercompany Dividend Proceeds - Investing														81	[2]	70	[4]	(60)	[6]
Cash Flows from Financing Activities
Intercompany Dividend Proceeds - Financing														$ 81	[2]	$ 70	[4]	$ 60	[6]

[1] All significant intercompany transactions have been eliminated in consolidation.

[2] All significant intercompany transactions have been eliminated in consolidation.

[3] All significant intercompany transactions have been eliminated in consolidation.

[4] All significant intercompany transactions have been eliminated in consolidation.

[5] All significant intercompany transactions have been eliminated in consolidation.

[6] All significant intercompany transactions have been eliminated in consolidation.

[7] All significant intercompany transactions have been eliminated in consolidation.

[8] All significant intercompany transactions have been eliminated in consolidation.