Asset Impairment Expense (Narrative) (Details) - USD ($) $ in Millions		3 Months Ended					12 Months Ended
		Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use							$ 185	$ 208	$ 537
Other Asset Impairment Charges		$ 69	$ 116	$ 42	$ 74	$ 92	185	208	537
Hawaii Subsidiary [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use							60	0	0
Kilroot and Ballylumford [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use							115	0	37
Assets carrying amount		114					114
Shady Point [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use							0	157	0
Assets carrying amount				30				30
Nejapa [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use							0	37	0
Assets carrying amount				$ 5				5
DPL Subsidiary [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use							0	0	175
Laurel Mountain [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use							0	0	121
Kazakhstan Hydro [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets to be Disposed of							0	0	92
Kazakhstan [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets to be Disposed of							0	0	94
Long Lived Assets Held For Sale [Member] | Kilroot and Ballylumford [Member]
Asset Impairment Expense [Line Items]
Other Asset Impairment Charges	[1]						115
Assets carrying amount			$ 232
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Stuart Station [Member]
Asset Impairment Expense [Line Items]
Assets carrying amount									3
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Killen Station [Member]
Asset Impairment Expense [Line Items]
Assets carrying amount									8
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] | DPL Peaking Generation [Domain]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets to be Disposed of									109
Assets carrying amount									346
Fair Value Less Costs To Sell									237
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					190
Disposal Group, Including Discontinued Operation, Foreign Currency Translation Gains (Losses)									100
Fair Value Less Costs To Sell		92					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
Long Lived Assets Held And Used [Member] | Hawaii Subsidiary [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use							60
Assets carrying amount		103					103
Long Lived Assets Held And Used [Member] | Kilroot [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use								37
Assets carrying amount		$ 20					$ 20
Long Lived Assets Held And Used [Member] | Shady Point [Member]
Asset Impairment Expense [Line Items]
Other Asset Impairment Charges	[1]							157
Long Lived Assets Held And Used [Member] | Nejapa [Member]
Asset Impairment Expense [Line Items]
Other Asset Impairment Charges	[2]							$ 37
Long Lived Assets Held And Used [Member] | Laurel Mountain [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use									121
Assets carrying amount									$ 33

[1] 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 22—Asset Impairment Expense and Note 25—Held-for-Sale and Dispositions for further information.

[2] See Note 22—Asset Impairment Expense for further information.