Fair Value (Nonrecurring Measurements) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017	Jun. 30, 2016
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset Impairment Charges		$ 0	$ 168
Other Asset Impairment Charges		$ 0	168
Long Lived Assets Held And Used [Member] | DPL Subsidiary [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Other Asset Impairment Charges	[1]		66
Long Lived Assets Held And Used [Member] | Other Subsidiaries [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Other Asset Impairment Charges	[1]		8
Long Lived Assets Held And Used [Member] | Kazakhstan [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Other Asset Impairment Charges	[1]		$ 94
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	[1]			$ 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	[1]			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	[1]			11
Long Lived Assets Held And Used [Member] | Fair Value [Member] | Other Subsidiaries [Member] | Level 1 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[1]			0
Long Lived Assets Held And Used [Member] | Fair Value [Member] | Other Subsidiaries [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[1]			0
Long Lived Assets Held And Used [Member] | Fair Value [Member] | Other Subsidiaries [Member] | Level 3 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[1]			7
Long Lived Assets Held And Used [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 And Used [Member] | Fair Value [Member] | Kazakhstan [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[1]			29
Long Lived Assets Held And Used [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 And Used [Member] | Carrying Amount [Member] | DPL Subsidiary [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[1],[2]			77
Long Lived Assets Held And Used [Member] | Carrying Amount [Member] | Other Subsidiaries [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[1],[2]			15
Long Lived Assets Held And Used [Member] | Carrying Amount [Member] | Kazakhstan [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	[1],[2]			$ 171
Disposal Group, Disposed of by Means Other than Sale, Not Discontinued Operations [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 Revenue Growth Rate		26.00%
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent		(10.00%)
Fair Value Inputs, Discount Rate		17.00%
Disposal Group, Disposed of by Means Other than Sale, Not Discontinued Operations [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 Revenue Growth Rate		110.00%
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent		(11.00%)
Disposal Group, Disposed of by Means Other than Sale, Not Discontinued Operations [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 Revenue Growth Rate		3.00%
Fair Value Inputs, Long-term Pre-tax Operating Margin, Percent		(22.00%)

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

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