Derivative Instruments and Hedging Activities - Intro (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Master Netting Arrangements (Numeric) [Line Items]
Cash Collateral Obligation Under Master Netting Arrangement	$ 28	$ 20
Cash collateral posted under master netting arrangements	0	0
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	0	0
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	0	0
Kentucky Utilities Co [Member]
Master Netting Arrangements (Numeric) [Line Items]
Cash Collateral Obligation Under Master Netting Arrangement	0	0
Cash collateral posted under master netting arrangements	$ 0	$ 0