Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Income Tax Provision [Line Items]
Income (Loss) Before Income Taxes	$ 142	$ (400)	$ 393	$ (268)
Income Taxes	$ 54	$ 1	$ 157	$ 11
Effective Tax Rate	38.00%	0.00%	40.00%	(4.00%)
Annualized effective tax rate			39.65%	31.81%
Tax benefit from settlement of previously unrecognized tax benefits				$ 12
Tax benefit from state deferred tax liabilities				17
Talen Energy Supply
Income Tax Provision [Line Items]
Income (Loss) Before Income Taxes	$ 144	$ (400)	$ 406	(268)
Income Taxes	$ 55	$ 1	$ 162	$ 11
Effective Tax Rate	38.00%	0.00%	40.00%	(4.00%)

Effective Income Tax Rate Reconciliation, Interim Period, Annualized Percent

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Effective Income Tax Reconciliation, State Deferred Tax Change, Amount

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[Line Items] for Income Tax Provision [Table]

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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Amount of income (loss) from continuing operations before deduction of income tax expense (benefit) and income (loss) attributable to noncontrolling interest, and addition of income (loss) from equity method investments.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Amount of increase (decrease) to previously recorded tax expense. Includes, but is not limited to, significant settlements of income tax disputes, and unusual tax positions or infrequent actions taken by the entity, including tax assessment reversal, and IRS tax settlement.

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