Derivative Instruments and Hedging Activities - Intro (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Master Netting Arrangements (Numeric) [Line Items]
Cash collateral posted under master netting arrangements	$ 8	$ 9
LG And E And KU Energy LLC [Member]
Master Netting Arrangements (Numeric) [Line Items]
Cash collateral posted under master netting arrangements	8	9
Louisville Gas And Electric Co [Member]
Master Netting Arrangements (Numeric) [Line Items]
Cash collateral posted under master netting arrangements	$ 8	$ 9