Fair Value (Nonrecurring Measurements) (Details) - USD ($)		3 Months Ended		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Aug. 31, 2016	Jun. 30, 2016	Mar. 31, 2016	Aug. 28, 2015	Jun. 30, 2015	Feb. 09, 2015
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset Impairment Charges				$ 475,000,000	$ 276,000,000
Other Asset Impairment Charges		$ 79,000,000	$ 231,000,000	473,000,000	276,000,000
buffalo gap III [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring			116,000,000		116,000,000
Kilroot [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring			78,000,000		78,000,000
UK Wind Projects [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring										$ 1,000,000
Discontinued operations and held for sale businesses [Member] | Sul Subsidiary [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[1]						$ 470,000,000
Other Asset Impairment Charges	[1]			783,000,000
Discontinued operations and held for sale businesses [Member] | Fair Value [Member] | Sul Subsidiary [Member] | Level 1 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[1]						0
Discontinued operations and held for sale businesses [Member] | Carrying Amount [Member] | Sul Subsidiary [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[1],[2]						1,581,000,000
Long Lived Assets Held And Used [Member] | buffalo gap III [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset Impairment Charges	[3]				118,000,000
Long Lived Assets Held And Used [Member] | Kilroot [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset Impairment Charges	[3]				113,000,000
Long Lived Assets Held And Used [Member] | DPL Subsidiary [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Other Asset Impairment Charges	[3]			235,000,000
Long Lived Assets Held And Used [Member] | buffalo gap II [Member] [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring								$ 92,000,000
Other Asset Impairment Charges	[3]			159,000,000
Long Lived Assets Held And Used [Member] | UK Wind Projects [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset Impairment Charges	[3]				37,000,000
Long Lived Assets Held And Used [Member] | Other Entity [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Other Asset Impairment Charges	[3]				8,000,000
Long Lived Assets Held And Used [Member] | Buffalo Gap [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Other Asset Impairment Charges	[3]			78,000,000
Long Lived Assets Held And Used [Member] | Fair Value [Member] | buffalo gap III [Member] | Level 1 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[3]		0		0
Long Lived Assets Held And Used [Member] | Fair Value [Member] | buffalo gap III [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[3]		0		0
Long Lived Assets Held And Used [Member] | Fair Value [Member] | buffalo gap III [Member] | Level 3 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[3]		116,000,000		116,000,000
Long Lived Assets Held And Used [Member] | Fair Value [Member] | Kilroot [Member] | Level 1 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[3]								$ 0
Long Lived Assets Held And Used [Member] | Fair Value [Member] | Kilroot [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[3]								0
Long Lived Assets Held And Used [Member] | Fair Value [Member] | Kilroot [Member] | Level 3 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[3]								78,000,000
Long Lived Assets Held And Used [Member] | Fair Value [Member] | DPL Subsidiary [Member] | Level 1 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[3]						0
Long Lived Assets Held And Used [Member] | Fair Value [Member] | DPL Subsidiary [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[3]						0
Long Lived Assets Held And Used [Member] | Fair Value [Member] | buffalo gap II [Member] [Member] | Level 1 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[3]							0
Long Lived Assets Held And Used [Member] | Fair Value [Member] | buffalo gap II [Member] [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[3]							0
Long Lived Assets Held And Used [Member] | Fair Value [Member] | UK Wind Projects [Member] | Level 1 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[3]									0
Long Lived Assets Held And Used [Member] | Fair Value [Member] | UK Wind Projects [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[3]									1,000,000
Long Lived Assets Held And Used [Member] | Fair Value [Member] | UK Wind Projects [Member] | Level 3 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[3]									0
Long Lived Assets Held And Used [Member] | Fair Value [Member] | Other Entity [Member] | Level 1 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[3]		0		0
Long Lived Assets Held And Used [Member] | Fair Value [Member] | Other Entity [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[3]		21,000,000		21,000,000
Long Lived Assets Held And Used [Member] | Fair Value [Member] | Other Entity [Member] | Level 3 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[3]		0		0
Long Lived Assets Held And Used [Member] | Fair Value [Member] | Buffalo Gap [Member] | Level 1 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[3]					$ 0
Long Lived Assets Held And Used [Member] | Fair Value [Member] | Buffalo Gap [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[3]					0
Long Lived Assets Held And Used [Member] | Carrying Amount [Member] | buffalo gap III [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[2],[3]		234,000,000		234,000,000
Long Lived Assets Held And Used [Member] | Carrying Amount [Member] | Kilroot [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[2],[3]								$ 191,000,000
Long Lived Assets Held And Used [Member] | Carrying Amount [Member] | DPL Subsidiary [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[2],[3]						324,000,000
Long Lived Assets Held And Used [Member] | Carrying Amount [Member] | buffalo gap II [Member] [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[2],[3]							251,000,000
Long Lived Assets Held And Used [Member] | Carrying Amount [Member] | UK Wind Projects [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[2],[3]									$ 38,000,000
Long Lived Assets Held And Used [Member] | Carrying Amount [Member] | Other Entity [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[2],[3]		$ 29,000,000		29,000,000
Long Lived Assets Held And Used [Member] | Carrying Amount [Member] | Buffalo Gap [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[2],[3]					113,000,000
Equity Method Investments [Member] | Solar Spain [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Other Nonoperating Expense					$ 0
Equity Method Investments [Member] | Fair Value [Member] | Solar Spain [Member] | Level 1 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring											$ 0
Equity Method Investments [Member] | Fair Value [Member] | Solar Spain [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring											0
Equity Method Investments [Member] | Fair Value [Member] | Solar Spain [Member] | Level 3 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring											29,000,000
Equity Method Investments [Member] | Carrying Amount [Member] | Solar Spain [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[2]										$ 29,000,000
Discontinued Operations, Held-for-sale [Member] | Discontinued operations and held for sale businesses [Member] | Fair Value [Member] | Sul Subsidiary [Member] | Level 3 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[1]						0
Long Lived Assets Held And Used [Member] | buffalo gap II [Member] [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[3]							$ 92,000,000
Long Lived Assets Held And Used [Member] | Fair Value [Member] | Buffalo Gap [Member] | Level 3 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[3]					$ 35,000,000
Long Lived Assets Held And Used [Member] | Long Lived Assets Held And Used [Member] | Fair Value [Member] | DPL Subsidiary [Member] | Level 3 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring							$ 89,000,000
Long Lived Assets Held And Used [Member] | Long Lived Assets Held And Used [Member] | Fair Value [Member] | buffalo gap II [Member] [Member] | Level 3 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring		$ 92,000,000		$ 92,000,000
Long Lived Assets Held And Used [Member] | Income Approach Valuation Technique [Member] | Weighted Average [Member] | DPL Subsidiary [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Fair Value Inputs, Long-term Revenue Growth Rate				(1.00%)
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent				5.00%
Long Lived Assets Held And Used [Member] | Income Approach Valuation Technique [Member] | Weighted Average [Member] | buffalo gap II [Member] [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Fair Value Inputs, Long-term Revenue Growth Rate				20.00%
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent				18.00%
Fair Value Inputs, Discount Rate				9.00%
Long Lived Assets Held And Used [Member] | Income Approach Valuation Technique [Member] | Weighted Average [Member] | Buffalo Gap [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Fair Value Inputs, Long-term Revenue Growth Rate				(14.00%)
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent				29.00%
Fair Value Inputs, Discount Rate				9.00%
Long Lived Assets Held And Used [Member] | Income Approach Valuation Technique [Member] | Maximum [Member] | DPL Subsidiary [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Fair Value Inputs, Long-term Revenue Growth Rate				13.00%
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent				60.00%
Fair Value Inputs, Discount Rate				12.00%
Long Lived Assets Held And Used [Member] | Income Approach Valuation Technique [Member] | Maximum [Member] | buffalo gap II [Member] [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Fair Value Inputs, Long-term Revenue Growth Rate				21.00%
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent				48.00%
Long Lived Assets Held And Used [Member] | Income Approach Valuation Technique [Member] | Maximum [Member] | Buffalo Gap [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Fair Value Inputs, Long-term Revenue Growth Rate				9.00%
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent				42.00%
Long Lived Assets Held And Used [Member] | Income Approach Valuation Technique [Member] | Minimum [Member] | DPL Subsidiary [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Fair Value Inputs, Long-term Revenue Growth Rate				(11.00%)
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent				(50.00%)
Fair Value Inputs, Discount Rate				7.00%
Long Lived Assets Held And Used [Member] | Income Approach Valuation Technique [Member] | Minimum [Member] | buffalo gap II [Member] [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Fair Value Inputs, Long-term Revenue Growth Rate				(17.00%)
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent				(166.00%)
Long Lived Assets Held And Used [Member] | Income Approach Valuation Technique [Member] | Minimum [Member] | Buffalo Gap [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Fair Value Inputs, Long-term Revenue Growth Rate				(20.00%)
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent				(40.00%)

[1] (3) Per the Company’s policy, pre-tax loss is limited to the impairment of long-lived assets. Any additional loss will be recognized on completion of the sale. See Note 16—Discontinued Operations for further information.

[2] (1) Represents the carrying values at the dates of measurement, before fair value adjustment.

[3] See Note 14—Asset Impairment Expense for further information.