Derivative Instruments and Hedging Activities (Intro) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Master Netting Arrangements (Numeric) [Line Items]
Obligation to return cash collateral obligation under master netting arrangement	$ 15
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