Asset Impairment Expense (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2017	Mar. 31, 2017	Sep. 30, 2018	Sep. 30, 2017
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use	$ 74		$ 2		$ 166	$ 260
US Generation Facility [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use	73	$ 83	0		156	0
Kazakhstan Hydro [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets to be Disposed of	0		2		0	92
Kazakhstan [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets to be Disposed of	0		0		0	94
DPL Subsidiary [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use	0		0		0	66
Other Subsidiaries [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use	1		0		10	8
Long Lived Assets Held For Sale [Member] | Kazakhstan Hydro [Member]
Asset Impairment Expense [Line Items]
Assets Carrying Amount Disclosure Nonrecurring			190			190
Disposal Group, Including Discontinued Operation, Foreign Currency Translation Gains (Losses)						100
Fair Value Less Costs To Sell			$ 92			$ 92
Long Lived Assets Held For Sale [Member] | Kazakhstan [Member]
Asset Impairment Expense [Line Items]
Assets Carrying Amount Disclosure Nonrecurring				$ 171
Disposal Group, Including Discontinued Operation, Foreign Currency Translation Gains (Losses)				92
Fair Value Less Costs To Sell				29
Impairment of Long-Lived Assets to be Disposed of				94
Fair Value, Measurements, Nonrecurring [Member] | Long Lived Assets Held And Used [Member] | US Generation Facility [Member]
Asset Impairment Expense [Line Items]
Assets, fair value	$ 55	$ 127			$ 55
Fair Value, Measurements, Nonrecurring [Member] | Long Lived Assets Held And Used [Member] | Stuart Station [Member]
Asset Impairment Expense [Line Items]
Assets, fair value				3
Fair Value, Measurements, Nonrecurring [Member] | Long Lived Assets Held And Used [Member] | Killen Station [Member]
Asset Impairment Expense [Line Items]
Assets, fair value				$ 8