Goodwill and Other Intangible Assets (Goodwill) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Changes in the Carrying Amount of Goodwill by Segment [Roll Forward]
Balance at beginning of period	$ 3,060	$ 3,550
Effect of foreign currency exchange rates	198	(490)
Balance at end of period	3,258	3,060
U.K. Regulated [Member]
Changes in the Carrying Amount of Goodwill by Segment [Roll Forward]
Balance at beginning of period	2,398	2,888
Effect of foreign currency exchange rates	198	(490)
Balance at end of period	2,596	2,398
Kentucky Regulated [Member]
Changes in the Carrying Amount of Goodwill by Segment [Roll Forward]
Balance at beginning of period	662	662
Balance at end of period	662	662
LG And E And KU Energy LLC [Member]
Changes in the Carrying Amount of Goodwill by Segment [Roll Forward]
Balance at beginning of period	996
Balance at end of period	996	996
Louisville Gas And Electric Co [Member]
Changes in the Carrying Amount of Goodwill by Segment [Roll Forward]
Balance at beginning of period	389
Balance at end of period	389	389
Kentucky Utilities Co [Member]
Changes in the Carrying Amount of Goodwill by Segment [Roll Forward]
Balance at beginning of period	607
Balance at end of period	$ 607	$ 607