Derivative Instruments and Hedging Activities - Gains and Losses (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Interest Expense	$ 259	$ 244	$ 746	$ 718
Other Income (Expense) - net	126	106	309	297
Cash Flow Hedges [Member]
Amounts Included in Income, OCI or Regulatory Liabilities/Assets [Abstract]
Gain (Loss) Reclassified from AOCI into Income	25	17	28	25
Cash Flow Hedges [Member] | Other Comprehensive Income (Loss) [Member]
Amounts Included in Income, OCI or Regulatory Liabilities/Assets [Abstract]
Derivative Gain (Loss) Recognized in OCI	19	27	39	26
Cash Flow Hedges [Member] | Interest Rate Swaps [Member] | Other Comprehensive Income (Loss) [Member]
Amounts Included in Income, OCI or Regulatory Liabilities/Assets [Abstract]
Derivative Gain (Loss) Recognized in OCI	(22)	0	(30)	0
Cash Flow Hedges [Member] | Interest Rate Swaps [Member] | Interest Expense [Member]
Amounts Included in Income, OCI or Regulatory Liabilities/Assets [Abstract]
Gain (Loss) Reclassified from AOCI into Income	(2)	(2)	(6)	(6)
Amount of gain (loss) reclassified from AOCI to income	(2)		(6)
Cash Flow Hedges [Member] | Interest Rate Swaps [Member] | Other Income (Expense) Net [Member]
Amounts Included in Income, OCI or Regulatory Liabilities/Assets [Abstract]
Amount of gain (loss) reclassified from AOCI to income	0		0
Cash Flow Hedges [Member] | Cross Currency Swaps [Member] | Other Comprehensive Income (Loss) [Member]
Amounts Included in Income, OCI or Regulatory Liabilities/Assets [Abstract]
Derivative Gain (Loss) Recognized in OCI	41	27	69	26
Cash Flow Hedges [Member] | Cross Currency Swaps [Member] | Interest Expense [Member]
Amounts Included in Income, OCI or Regulatory Liabilities/Assets [Abstract]
Gain (Loss) Reclassified from AOCI into Income		1		1
Amount of gain (loss) reclassified from AOCI to income	0		0
Hedged items	0		0
Cash Flow Hedges [Member] | Cross Currency Swaps [Member] | Other Income (Expense) Net [Member]
Amounts Included in Income, OCI or Regulatory Liabilities/Assets [Abstract]
Gain (Loss) Reclassified from AOCI into Income	27	18	34	30
Amount of gain (loss) reclassified from AOCI to income	27		34
Hedged items	(27)		(34)
Net Investment Hedges [Member] | Foreign Currency Contracts [Member] | Other Comprehensive Income (Loss) [Member]
Amounts Included in Income, OCI or Regulatory Liabilities/Assets [Abstract]
Derivative Gain (Loss) Recognized in OCI	0	0	1	11
Not Designated As Hedging Instruments [Member]
Amounts Included in Income, OCI or Regulatory Liabilities/Assets [Abstract]
Gain (loss) recognized in income on derivative	43	39	53	88
Not Designated As Hedging Instruments [Member] | Interest Rate Swaps [Member] | Regulatory Assets Noncurrent [Member]
Amounts Included in Income, OCI or Regulatory Liabilities/Assets [Abstract]
Gain (loss) recognized as regulatory liabilities/assets	(2)	2	(5)	7
Not Designated As Hedging Instruments [Member] | Interest Rate Swaps [Member] | Interest Expense [Member]
Amounts Included in Income, OCI or Regulatory Liabilities/Assets [Abstract]
Gain (loss) recognized in income on derivative	(1)	(1)	(3)	(4)
Not Designated As Hedging Instruments [Member] | Foreign Currency Contracts [Member] | Other Income (Expense) Net [Member]
Amounts Included in Income, OCI or Regulatory Liabilities/Assets [Abstract]
Gain (loss) recognized in income on derivative	44	40	56	92
LG And E And KU Energy LLC [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Interest Expense	57	52	169	154
Other Income (Expense) - net	2	0	2	(2)
LG And E And KU Energy LLC [Member] | Not Designated As Hedging Instruments [Member] | Interest Rate Swaps [Member] | Regulatory Assets Noncurrent [Member]
Amounts Included in Income, OCI or Regulatory Liabilities/Assets [Abstract]
Gain (loss) recognized as regulatory liabilities/assets	(2)	2	(5)	7
LG And E And KU Energy LLC [Member] | Not Designated As Hedging Instruments [Member] | Interest Rate Swaps [Member] | Interest Expense [Member]
Amounts Included in Income, OCI or Regulatory Liabilities/Assets [Abstract]
Gain (loss) recognized in income on derivative	(1)	(1)	(3)	(4)
Louisville Gas And Electric Co [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Interest Expense	22	20	65	57
Other Income (Expense) - net	0	(3)	(1)	(5)
Louisville Gas And Electric Co [Member] | Not Designated As Hedging Instruments [Member] | Interest Rate Swaps [Member] | Regulatory Assets Noncurrent [Member]
Amounts Included in Income, OCI or Regulatory Liabilities/Assets [Abstract]
Gain (loss) recognized as regulatory liabilities/assets	(2)	2	(5)	7
Louisville Gas And Electric Co [Member] | Not Designated As Hedging Instruments [Member] | Interest Rate Swaps [Member] | Interest Expense [Member]
Amounts Included in Income, OCI or Regulatory Liabilities/Assets [Abstract]
Gain (loss) recognized in income on derivative	(1)	(1)	(3)	(4)
Kentucky Utilities Co [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Interest Expense	28	24	82	74
Other Income (Expense) - net	$ 4	$ 1	$ 4	$ 1