Fair Value (Nonrecurring Measurements) (Details) - USD ($)		2 Months Ended	3 Months Ended
		Feb. 28, 2017	Mar. 31, 2017	Mar. 31, 2016
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset Impairment Charges			$ 168,000,000	$ 161,000,000
Other Asset Impairment Charges			168,000,000	159,000,000
Long Lived Assets Held For Sale [Member] | Kazakhstan [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Other Asset Impairment Charges	[1]		94,000,000
Long Lived Assets Held For Sale [Member] | Fair Value [Member] | Kazakhstan [Member] | Level 1 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[1]		0
Long Lived Assets Held For Sale [Member] | Fair Value [Member] | Kazakhstan [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[1]		29,000,000
Long Lived Assets Held For Sale [Member] | Fair Value [Member] | Kazakhstan [Member] | Level 3 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[1]		0
Long Lived Assets Held For Sale [Member] | Carrying Amount [Member] | Kazakhstan [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[1],[2]		171,000,000
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]	$ 66,000,000
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] | Energy Storage [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] | 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] | DPL Subsidiary [Member] | Level 3 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[3]	11,000,000
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] | buffalo gap II [Member] [Member] | Level 3 [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] | Energy Storage [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] | Energy Storage [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] | Energy Storage [Member] | Level 3 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[3]		7,000,000
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]	$ 77,000,000
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] | Energy Storage [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[2],[3]		$ 15,000,000
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 Pre-tax Operating Margin, Percent			15.00%
Fair Value Inputs, Discount Rate			7.00%
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
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent
Fair Value Inputs, Discount Rate
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
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent
Fair Value Inputs, Discount Rate
Long Lived Assets Held And Used [Member] | Income Approach Valuation Technique [Member] | Weighted Average [Member] | Energy Storage [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent			80.00%
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 Pre-tax Operating Margin, Percent			22.00%
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
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent
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
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent
Long Lived Assets Held And Used [Member] | Income Approach Valuation Technique [Member] | Maximum [Member] | Energy Storage [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent			85.00%
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 Pre-tax Operating Margin, Percent			10.00%
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
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent
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
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent
Long Lived Assets Held And Used [Member] | Income Approach Valuation Technique [Member] | Minimum [Member] | Energy Storage [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent			46.00%

[1] (3) Per the Company’s policy, pretax loss is limited to the impairment of long-lived assets. Any additional loss will be recognized on completion of the sale. See Note 16—Held-for-Sale Businesses and Dispositions for further information

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

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