Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Income Tax Provision [Line Items]
Income (Loss) Before Income Taxes	$ (6)	$ (17)	$ 251	$ 132
Income Taxes	$ (3)	$ (43)	$ 103	$ 10
Effective Tax Rate (as a percent)	50.00%	253.00%	41.00%	8.00%
Annualized effective tax rate (as a percent)			39.87%	32.52%
Settlement of previously unrecognized tax benefits		$ 12		$ 12
State deferred tax liabilities		17		17
Talen Energy Supply
Income Tax Provision [Line Items]
Income (Loss) Before Income Taxes	$ 5	(17)	$ 262	132
Income Taxes	$ 1	$ (43)	$ 107	$ 10
Effective Tax Rate (as a percent)	20.00%	253.00%	41.00%	8.00%

Effective Income Tax Rate Reconciliation, Interim Period, Annualized Percent

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[Line Items] for Income Tax Provision [Table]

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Amount of deferred state and local tax expense (benefit) pertaining to income (loss) from continuing operations.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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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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Sum of operating profit and nonoperating income or expense before Income or Loss from equity method investments, income taxes, extraordinary items, and noncontrolling interest.

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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 the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to income tax settlements. Including, but not limited to, domestic tax settlement, foreign tax settlement, state and local tax settlement, and other tax settlements.

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