Derivative Instruments and Hedging Activities (Intro) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Master Netting Arrangements (Numeric) [Line Items]
Cash Collateral Obligation Under Master Netting Arrangement	$ 20	$ 19
Cash Collateral Posted Under Master Netting Arrangements	0	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	0	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	0	3
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