Derivative Instruments and Hedging Activities - Intro (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Master Netting Arrangements (Numeric) [Line Items]
Cash collateral obligation under master netting arrangements	$ 17	$ 40
Cash colleteral 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 arrangements	0	0
Cash colleteral 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 arrangements	0	0
Cash colleteral posted under master netting arrangements	0	0
Kentucky Utilities Co [Member]
Master Netting Arrangements (Numeric) [Line Items]
Cash collateral obligation under master netting arrangements	0	0
Cash colleteral posted under master netting arrangements	$ 0	$ 0