Goodwill and Other Intangible Assets (Goodwill) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Changes in the Carrying Amount of Goodwill by Segment [Roll Forward]
Balance at beginning of period	$ 3,162	$ 3,258
Effect of foreign currency exchange rates	34	(149)
Goodwill recognized during the period	0	53
Other	2	0
Balance at end of period	3,198	3,162
U.K. Regulated [Member]
Changes in the Carrying Amount of Goodwill by Segment [Roll Forward]
Balance at beginning of period	2,447	2,596
Effect of foreign currency exchange rates	34	(149)
Goodwill recognized during the period	0	0
Other	2	0
Balance at end of period	2,483	2,447
Kentucky Regulated [Member]
Changes in the Carrying Amount of Goodwill by Segment [Roll Forward]
Balance at beginning of period	662	662
Effect of foreign currency exchange rates	0	0
Goodwill recognized during the period	0	0
Other	0	0
Balance at end of period	662	662
Corporate And Other [Member]
Changes in the Carrying Amount of Goodwill by Segment [Roll Forward]
Balance at beginning of period	53	0
Effect of foreign currency exchange rates	0	0
Goodwill recognized during the period	0	53
Other	0	0
Balance at end of period	$ 53	$ 53