Asset Impairment Expense (Narrative) (Details) - USD ($) $ in Millions		3 Months Ended							6 Months Ended	9 Months Ended	12 Months Ended
		Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Mar. 31, 2017	Mar. 31, 2016	Jun. 30, 2016	Sep. 30, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use											$ 208	$ 537	$ 1,096
Other Asset Impairment Charges		$ 42	$ 74	$ 92	$ 277	$ 90	$ 168				208	537	1,096
Shady Point [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use											157	0	0
Assets carrying amount		30									30
Nejapa [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use											37	0	0
Assets carrying amount		5									5
Laurel Mountain [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use											0	121	0
Kazakhstan Hydro [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets to be Disposed of											0	92	0
Kazakhstan [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets to be Disposed of											0	94	0
Buffalo Gap I
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use											0	0	77
DPL Subsidiary [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use											0	175	859
buffalo gap II [Member] [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use											0	0	159
Kilroot [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use											0	37	$ 0
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Kazakhstan Hydro [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets to be Disposed of											92
Assets carrying amount						190
Disposal Group, Including Discontinued Operation, Foreign Currency Translation Gains (Losses)				$ 100
Fair Value Less Costs To Sell						$ 92
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Kazakhstan [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets to be Disposed of											94
Assets carrying amount							171
Disposal Group, Including Discontinued Operation, Foreign Currency Translation Gains (Losses)											92
Fair Value Less Costs To Sell							$ 29
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | DPL Peaking Generation [Domain]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets to be Disposed of											109
Assets carrying amount		346									346
Fair Value Less Costs To Sell		237									237
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | DPL Subsidiary [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets to be Disposed of											66
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Stuart Station [Member]
Asset Impairment Expense [Line Items]
Assets carrying amount		3									3
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Killen Station [Member]
Asset Impairment Expense [Line Items]
Assets carrying amount		8									8
Long Lived Assets Held And Used [Member]
Asset Impairment Expense [Line Items]
Other Asset Impairment Charges	[1]											18
Long Lived Assets Held And Used [Member] | Parent Company [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use								$ 49		$ 23
Long Lived Assets Held And Used [Member] | Laurel Mountain [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use											121
Other Asset Impairment Charges	[1]											121
Assets carrying amount		33									33
Long Lived Assets Held And Used [Member] | Buffalo Gap I
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use												77
Assets carrying amount					36							36
Long Lived Assets Held And Used [Member] | Miami Fort [Domain]
Asset Impairment Expense [Line Items]
Assets carrying amount					36							36
Long Lived Assets Held And Used [Member] | Zimmer Station [Member]
Asset Impairment Expense [Line Items]
Assets carrying amount					24							24
Long Lived Assets Held And Used [Member] | DPL Peaking Generation [Domain]
Asset Impairment Expense [Line Items]
Assets carrying amount					2				$ 5			2
Long Lived Assets Held And Used [Member] | DPL Subsidiary [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use									235			624
Other Asset Impairment Charges	[1]											66
Long Lived Assets Held And Used [Member] | buffalo gap II [Member] [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use												159
Assets carrying amount					92							92
Long Lived Assets Held And Used [Member] | Stuart Station [Member]
Asset Impairment Expense [Line Items]
Assets carrying amount					57							57
Long Lived Assets Held And Used [Member] | Killen Station [Member]
Asset Impairment Expense [Line Items]
Assets carrying amount					43				$ 84			43
Long Lived Assets Held And Used [Member] | Kilroot [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use											37
Other Asset Impairment Charges	[1]											37
Assets carrying amount		$ 20									$ 20
Long Lived Assets Held And Used [Member] | Conesville DP&L
Asset Impairment Expense [Line Items]
Assets carrying amount					$ 1							$ 1

[1] See Note 20—Asset Impairment Expense for further information.