Asset Impairment Expense (Tables)

12 Months Ended

Dec. 31, 2017

Impairment or Disposal of Tangible Assets Disclosure [Abstract]

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

Year ended December 31, (in millions)	2017		2016		2015
DPL	$	175	$	859	$	—
Laurel Mountain	121		—		—
Kazakhstan Hydroelectric	92		—		—
Kazakhstan CHPs	94		—		—
Kilroot	37		—		121
Buffalo Gap II	—		159		—
Buffalo Gap I	—		77		—
Buffalo Gap III	—		—		116
U.K. Wind	—		—		37
Other	18		1		11
Total	$	537	$	1,096	$	285