Derivative Instruments and Hedging Activities (Offseting Derivative Instruments and Credit Risk-Related Features) (Details) - USD ($) $ in Millions		Mar. 31, 2016	Dec. 31, 2015
Credit Risk-Related Contingent Features [Abstract]
Aggregate fair value of derivative instruments in a net liability position with credit risk-related contingent features		$ 31
Aggregate fair value of collateral posted on these derivative instruments		8
Aggregate fair value of additional collateral requirements in the event of a credit downgrade below investment grade	[1]	23
Treasury Derivatives [Member]
Offsetting Assets And Liabilities [Line Items]
Gross assets		437	$ 295
Derivative instruments eligible for offset - assets		45	25
Cash collateral received eligible for offset - assets		15	0
Net assets		377	270
Gross liabilities		98	72
Derivative instruments eligible for offset - liabilities		45	25
Cash collateral pledged eligible for offset - liabilities		8	9
Net liabilities		45	38
LG And E And KU Energy LLC [Member]
Credit Risk-Related Contingent Features [Abstract]
Aggregate fair value of derivative instruments in a net liability position with credit risk-related contingent features		30
Aggregate fair value of collateral posted on these derivative instruments		8
Aggregate fair value of additional collateral requirements in the event of a credit downgrade below investment grade	[1]	22
LG And E And KU Energy LLC [Member] | Treasury Derivatives [Member]
Offsetting Assets And Liabilities [Line Items]
Gross assets		0	0
Derivative instruments eligible for offset - assets		0	0
Cash collateral received eligible for offset - assets		0	0
Net assets		0	0
Gross liabilities		53	47
Derivative instruments eligible for offset - liabilities		0	0
Cash collateral pledged eligible for offset - liabilities		8	9
Net liabilities		45	38
Louisville Gas And Electric Co [Member]
Credit Risk-Related Contingent Features [Abstract]
Aggregate fair value of derivative instruments in a net liability position with credit risk-related contingent features		30
Aggregate fair value of collateral posted on these derivative instruments		8
Aggregate fair value of additional collateral requirements in the event of a credit downgrade below investment grade	[1]	22
Louisville Gas And Electric Co [Member] | Treasury Derivatives [Member]
Offsetting Assets And Liabilities [Line Items]
Gross assets		0	0
Derivative instruments eligible for offset - assets		0	0
Cash collateral received eligible for offset - assets		0	0
Net assets		0	0
Gross liabilities		53	47
Derivative instruments eligible for offset - liabilities		0	0
Cash collateral pledged eligible for offset - liabilities		8	9
Net liabilities		$ 45	$ 38

[1] Includes the effect of net receivables and payables alread y recorded on the Balance Sheet.