Segment and Related Information (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Income Statement Data [Abstract]
Revenues		$ 1,889	$ 1,878	$ 5,685	$ 5,889
Net income		473	393	1,437	283
Balance Sheet Data [Abstract]
Assets		38,038		38,038		$ 39,301
United Kingdom Regulated [Member]
Income Statement Data [Abstract]
Revenues		515	552	1,673	1,836
Net income	[1]	281	249	915	814
Balance Sheet Data [Abstract]
Assets	[2]	15,014		15,014		16,669
Segment (Numeric) [Abstract]
Net property, plant and equipment not subject to accounting for the effects of certain types of regulation		11,100		11,100		12,200
Kentucky Regulated [Member]
Income Statement Data [Abstract]
Revenues		835	801	2,382	2,414
Net income		126	111	314	267
Balance Sheet Data [Abstract]
Assets		13,853		13,853		13,756
Pennsylvania Regulated [Member]
Income Statement Data [Abstract]
Revenues		539	519	1,619	1,625
Net income		91	55	263	191
Balance Sheet Data [Abstract]
Assets		9,070		9,070		8,511
Corporate And Other [Member]
Income Statement Data [Abstract]
Revenues		0	6	11	14
Net income		(25)	(19)	(55)	(74)
Balance Sheet Data [Abstract]
Assets	[3]	101		101		$ 365
Discontinued Operations [Member]
Income Statement Data [Abstract]
Net income	[4]	$ 0	$ (3)	$ 0	$ (915)

[1] Includes unrealized gains and losses from hedging foreign-currency related economic activity. See Note 14 for additional information.

[2] Includes $11.1 billion and $12.2 billion of net PP&E as of September 30, 2016 and December 31, 2015. WPD is not subject to accounting for the effects of certain types of regulation as prescribed by GAAP.

[3] Primarily consists of unallocated items, including cash, PP&E and the elimination of inter-segment transactions.

[4] See Note 8 for additional information.