Asset Impairment Expense (Tables)

12 Months Ended

Dec. 31, 2016

Impairment or Disposal of Tangible Assets Disclosure [Abstract]

Details of Impairment of Long-Lived Assets Held and Used by Asset

Years ended December 31, (in millions)	2016		2015		2014
DPL	$	859	$	—	$	—
Buffalo Gap II	159		—		—
Buffalo Gap I	77		—		—
Kilroot	—		121		—
Buffalo Gap III	—		116		—
U.K. Wind	—		37		12
Ebute	—		—		67
East Bend (DP&L)	—		—		12
Other	1		11		—
Total asset impairment expense	$	1,096	$	285	$	91