Derivative Instruments and Hedging Activities - Intro (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Master Netting Arrangements (Numeric) [Line Items]
Cash Collateral Obligation Under Master Netting Arrangement	$ 17	$ 19
Cash collateral posted under master netting arrangements	1	3
LG And E And KU Energy LLC [Member]
Master Netting Arrangements (Numeric) [Line Items]
Cash Collateral Obligation Under Master Netting Arrangement	0	0
Cash collateral posted under master netting arrangements	1	3
Louisville Gas And Electric Co [Member]
Master Netting Arrangements (Numeric) [Line Items]
Cash Collateral Obligation Under Master Netting Arrangement	0	0
Cash collateral posted under master netting arrangements	$ 1	$ 3