Derivative Instruments and Hedging Activities (Offseting Derivative Instruments and Credit Risk-Related Features) (Details) - USD ($) $ in Millions		Sep. 30, 2015	Dec. 31, 2014
Credit Risk-Related Contingent Features [Abstract]
Aggregate fair value of derivative instruments in a net liability position with credit risk-related contingent features		$ 32
Aggregate fair value of collateral posted on these derivative instruments		10
Aggregate fair value of additional collateral requirements in the event of a credit downgrade below investment grade	[1]	22
Treasury Derivatives [Member]
Offsetting Assets And Liabilities [Line Items]
Gross assets		231	$ 159
Derivative instruments eligible for offset - assets		33	65
Net assets		198	94
Gross liabilities		89	161
Derivative instruments eligible for offset - liabilities		33	65
Cash collateral pledged eligible for offset - liabilities		10	21
Net liabilities		46	75
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		10
Aggregate fair value of additional collateral requirements in the event of a credit downgrade below investment grade	[1]	20
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		50	114
Derivative instruments eligible for offset - liabilities		0	0
Cash collateral pledged eligible for offset - liabilities		10	20
Net liabilities		40	94
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		10
Aggregate fair value of additional collateral requirements in the event of a credit downgrade below investment grade	[1]	20
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		50	81
Derivative instruments eligible for offset - liabilities		0	0
Cash collateral pledged eligible for offset - liabilities		10	20
Net liabilities		$ 40	61
Kentucky Utilities Co [Member] | Treasury Derivatives [Member]
Offsetting Assets And Liabilities [Line Items]
Gross assets			0
Derivative instruments eligible for offset - assets			0
Cash collateral received eligible for offset - assets			0
Net assets			0
Gross liabilities			33
Derivative instruments eligible for offset - liabilities			0
Cash collateral pledged eligible for offset - liabilities			0
Net liabilities			$ 33

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