Asset Impairment Expense (Details) $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($) integer
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use		$ 79		$ 231	$ 473	$ 276
Kilroot [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use		0		113	0	113
Assets, fair value				78		78
buffalo gap III [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use		0		118	0	118
Assets, fair value				116		116
buffalo gap II [Member] [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use		0		0	159	0
Buffalo Gap [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use		78		0	78	0
UK Wind Projects [Member]
Asset Impairment Expense [Line Items]
number of projects no longer being pursued | integer							2
number of impaired projects | integer							4
Long-Lived Assets							$ 38
Impairment of Long-Lived Assets Held-for-use		0		0	0	37
Assets, fair value							$ 1
Other Impairment [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use		1		0	1	8
Parent Company [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use		23	$ 49
DPL Subsidiary [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use		0		$ 0	235	$ 0
Long Lived Assets Held And Used [Member] | Killen [Member] [Member]
Asset Impairment Expense [Line Items]
Assets, fair value		84			84
Long Lived Assets Held And Used [Member] | DPL Subsidiary [Member]
Asset Impairment Expense [Line Items]
Assets, fair value		$ 5			$ 5
Long Lived Assets Held And Used [Member] | buffalo gap II [Member] [Member]
Asset Impairment Expense [Line Items]
Assets, fair value			92
Long Lived Assets Held And Used [Member] | buffalo gap II [Member] [Member]
Asset Impairment Expense [Line Items]
Assets, fair value	[1]		$ 92

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