Derivative Instruments and Hedging Activities (Intro) (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Master Netting Arrangements (Numeric) [Line Items]
Cash collateral posted under master netting arrangements	$ 10	$ 21
LG And E And KU Energy LLC [Member]
Master Netting Arrangements (Numeric) [Line Items]
Cash collateral posted under master netting arrangements	10	21
Louisville Gas And Electric Co [Member]
Master Netting Arrangements (Numeric) [Line Items]
Cash collateral posted under master netting arrangements	$ 10	$ 21