Derivative Instruments and Hedging Activities - Fair Values (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Designated As Hedging Instruments [Member]
Fair Values by Balance Sheet Location [Abstract]
Asset value	$ 161	$ 135
Liability value	8	0
Designated As Hedging Instruments [Member] | Current Assets [Member]
Fair Values by Balance Sheet Location [Abstract]
Asset value	6	6
Designated As Hedging Instruments [Member] | Current Assets [Member] | Interest Rate Swaps [Member]
Fair Values by Balance Sheet Location [Abstract]
Asset value	0	0
Designated As Hedging Instruments [Member] | Current Assets [Member] | Cross Currency Swaps [Member]
Fair Values by Balance Sheet Location [Abstract]
Asset value	6	6
Designated As Hedging Instruments [Member] | Current Assets [Member] | Foreign Currency Contracts [Member]
Fair Values by Balance Sheet Location [Abstract]
Asset value	0	0
Designated As Hedging Instruments [Member] | Noncurrent Assets [Member]
Fair Values by Balance Sheet Location [Abstract]
Asset value	155	129
Designated As Hedging Instruments [Member] | Noncurrent Assets [Member] | Interest Rate Swaps [Member]
Fair Values by Balance Sheet Location [Abstract]
Asset value	0	0
Designated As Hedging Instruments [Member] | Noncurrent Assets [Member] | Cross Currency Swaps [Member]
Fair Values by Balance Sheet Location [Abstract]
Asset value	155	129
Designated As Hedging Instruments [Member] | Noncurrent Assets [Member] | Foreign Currency Contracts [Member]
Fair Values by Balance Sheet Location [Abstract]
Asset value	0	0
Designated As Hedging Instruments [Member] | Current Liabilities [Member]
Fair Values by Balance Sheet Location [Abstract]
Liability value	8	0
Designated As Hedging Instruments [Member] | Current Liabilities [Member] | Interest Rate Swaps [Member]
Fair Values by Balance Sheet Location [Abstract]
Liability value	8	0
Designated As Hedging Instruments [Member] | Current Liabilities [Member] | Cross Currency Swaps [Member]
Fair Values by Balance Sheet Location [Abstract]
Liability value	0	0
Designated As Hedging Instruments [Member] | Current Liabilities [Member] | Foreign Currency Contracts [Member]
Fair Values by Balance Sheet Location [Abstract]
Liability value	0	0
Designated As Hedging Instruments [Member] | Noncurrent Liabilities [Member]
Fair Values by Balance Sheet Location [Abstract]
Liability value	0	0
Designated As Hedging Instruments [Member] | Noncurrent Liabilities [Member] | Interest Rate Swaps [Member]
Fair Values by Balance Sheet Location [Abstract]
Liability value	0	0
Designated As Hedging Instruments [Member] | Noncurrent Liabilities [Member] | Cross Currency Swaps [Member]
Fair Values by Balance Sheet Location [Abstract]
Liability value	0	0
Designated As Hedging Instruments [Member] | Noncurrent Liabilities [Member] | Foreign Currency Contracts [Member]
Fair Values by Balance Sheet Location [Abstract]
Liability value	0	0
Not Designated As Hedging Instruments [Member]
Fair Values by Balance Sheet Location [Abstract]
Asset value	181	202
Liability value	23	22
Not Designated As Hedging Instruments [Member] | Current Assets [Member]
Fair Values by Balance Sheet Location [Abstract]
Asset value	127	103
Not Designated As Hedging Instruments [Member] | Current Assets [Member] | Interest Rate Swaps [Member]
Fair Values by Balance Sheet Location [Abstract]
Asset value	0	0
Not Designated As Hedging Instruments [Member] | Current Assets [Member] | Cross Currency Swaps [Member]
Fair Values by Balance Sheet Location [Abstract]
Asset value	0	0
Not Designated As Hedging Instruments [Member] | Current Assets [Member] | Foreign Currency Contracts [Member]
Fair Values by Balance Sheet Location [Abstract]
Asset value	127	103
Not Designated As Hedging Instruments [Member] | Noncurrent Assets [Member]
Fair Values by Balance Sheet Location [Abstract]
Asset value	54	99
Not Designated As Hedging Instruments [Member] | Noncurrent Assets [Member] | Interest Rate Swaps [Member]
Fair Values by Balance Sheet Location [Abstract]
Asset value	0	0
Not Designated As Hedging Instruments [Member] | Noncurrent Assets [Member] | Cross Currency Swaps [Member]
Fair Values by Balance Sheet Location [Abstract]
Asset value	0	0
Not Designated As Hedging Instruments [Member] | Noncurrent Assets [Member] | Foreign Currency Contracts [Member]
Fair Values by Balance Sheet Location [Abstract]
Asset value	54	99
Not Designated As Hedging Instruments [Member] | Current Liabilities [Member]
Fair Values by Balance Sheet Location [Abstract]
Liability value	5	6
Not Designated As Hedging Instruments [Member] | Current Liabilities [Member] | Interest Rate Swaps [Member]
Fair Values by Balance Sheet Location [Abstract]
Liability value	5	4
Not Designated As Hedging Instruments [Member] | Current Liabilities [Member] | Cross Currency Swaps [Member]
Fair Values by Balance Sheet Location [Abstract]
Liability value	0	0
Not Designated As Hedging Instruments [Member] | Current Liabilities [Member] | Foreign Currency Contracts [Member]
Fair Values by Balance Sheet Location [Abstract]
Liability value	0	2
Not Designated As Hedging Instruments [Member] | Noncurrent Liabilities [Member]
Fair Values by Balance Sheet Location [Abstract]
Liability value	18	16
Not Designated As Hedging Instruments [Member] | Noncurrent Liabilities [Member] | Interest Rate Swaps [Member]
Fair Values by Balance Sheet Location [Abstract]
Liability value	18	16
Not Designated As Hedging Instruments [Member] | Noncurrent Liabilities [Member] | Cross Currency Swaps [Member]
Fair Values by Balance Sheet Location [Abstract]
Liability value	0	0
Not Designated As Hedging Instruments [Member] | Noncurrent Liabilities [Member] | Foreign Currency Contracts [Member]
Fair Values by Balance Sheet Location [Abstract]
Liability value	0	0
LG And E And KU Energy LLC [Member] | Not Designated As Hedging Instruments [Member]
Fair Values by Balance Sheet Location [Abstract]
Asset value	0	0
Liability value	23	20
LG And E And KU Energy LLC [Member] | Not Designated As Hedging Instruments [Member] | Current Assets [Member]
Fair Values by Balance Sheet Location [Abstract]
Asset value	0	0
LG And E And KU Energy LLC [Member] | Not Designated As Hedging Instruments [Member] | Current Assets [Member] | Interest Rate Swaps [Member]
Fair Values by Balance Sheet Location [Abstract]
Asset value	0	0
LG And E And KU Energy LLC [Member] | Not Designated As Hedging Instruments [Member] | Noncurrent Assets [Member]
Fair Values by Balance Sheet Location [Abstract]
Asset value	0	0
LG And E And KU Energy LLC [Member] | Not Designated As Hedging Instruments [Member] | Noncurrent Assets [Member] | Interest Rate Swaps [Member]
Fair Values by Balance Sheet Location [Abstract]
Asset value	0	0
LG And E And KU Energy LLC [Member] | Not Designated As Hedging Instruments [Member] | Current Liabilities [Member]
Fair Values by Balance Sheet Location [Abstract]
Liability value	5	4
LG And E And KU Energy LLC [Member] | Not Designated As Hedging Instruments [Member] | Current Liabilities [Member] | Interest Rate Swaps [Member]
Fair Values by Balance Sheet Location [Abstract]
Liability value	5	4
LG And E And KU Energy LLC [Member] | Not Designated As Hedging Instruments [Member] | Noncurrent Liabilities [Member]
Fair Values by Balance Sheet Location [Abstract]
Liability value	18	16
LG And E And KU Energy LLC [Member] | Not Designated As Hedging Instruments [Member] | Noncurrent Liabilities [Member] | Interest Rate Swaps [Member]
Fair Values by Balance Sheet Location [Abstract]
Liability value	18	16
Louisville Gas And Electric Co [Member] | Not Designated As Hedging Instruments [Member]
Fair Values by Balance Sheet Location [Abstract]
Asset value	0	0
Liability value	23	20
Louisville Gas And Electric Co [Member] | Not Designated As Hedging Instruments [Member] | Current Assets [Member]
Fair Values by Balance Sheet Location [Abstract]
Asset value	0	0
Louisville Gas And Electric Co [Member] | Not Designated As Hedging Instruments [Member] | Current Assets [Member] | Interest Rate Swaps [Member]
Fair Values by Balance Sheet Location [Abstract]
Asset value	0	0
Louisville Gas And Electric Co [Member] | Not Designated As Hedging Instruments [Member] | Noncurrent Assets [Member]
Fair Values by Balance Sheet Location [Abstract]
Asset value	0	0
Louisville Gas And Electric Co [Member] | Not Designated As Hedging Instruments [Member] | Noncurrent Assets [Member] | Interest Rate Swaps [Member]
Fair Values by Balance Sheet Location [Abstract]
Asset value	0	0
Louisville Gas And Electric Co [Member] | Not Designated As Hedging Instruments [Member] | Current Liabilities [Member]
Fair Values by Balance Sheet Location [Abstract]
Liability value	5	4
Louisville Gas And Electric Co [Member] | Not Designated As Hedging Instruments [Member] | Current Liabilities [Member] | Interest Rate Swaps [Member]
Fair Values by Balance Sheet Location [Abstract]
Liability value	5	4
Louisville Gas And Electric Co [Member] | Not Designated As Hedging Instruments [Member] | Noncurrent Liabilities [Member]
Fair Values by Balance Sheet Location [Abstract]
Liability value	18	16
Louisville Gas And Electric Co [Member] | Not Designated As Hedging Instruments [Member] | Noncurrent Liabilities [Member] | Interest Rate Swaps [Member]
Fair Values by Balance Sheet Location [Abstract]
Liability value	$ 18	$ 16