Derivative Instruments and Hedging Activities (Gains and Losses) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Cash Flow Hedges [Member]
Amounts Included in Income, OCI or Regulatory Liabilities/Assets [Abstract]
Gain (loss) reclassified from AOCI into income on derivative (effective portion)	$ (13)	$ 15	$ 27	$ 0
Gain (loss) recognized in income on derivative (ineffective portion and amount excluded from effectiveness testing)	0	0	(70)	2
Cash Flow Hedges [Member] | Other Comprehensive Income [Member]
Amounts Included in Income, OCI or Regulatory Liabilities/Assets [Abstract]
Gain (loss) recognized in OCI on derivative (effective portion)	(30)	(7)	4	(83)
Cash Flow Hedges [Member] | Interest Rate Swaps [Member] | Other Comprehensive Income [Member]
Amounts Included in Income, OCI or Regulatory Liabilities/Assets [Abstract]
Gain (loss) recognized in OCI on derivative (effective portion)	(27)	(5)	(29)	(65)
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 on derivative (effective portion)	(2)	(5)	(9)	(14)
Gain (loss) recognized in income on derivative (ineffective portion and amount excluded from effectiveness testing)	0	0	0	2
Cash Flow Hedges [Member] | Cross Currency Swaps [Member] | Other Comprehensive Income [Member]
Amounts Included in Income, OCI or Regulatory Liabilities/Assets [Abstract]
Gain (loss) recognized in OCI on derivative (effective portion)	(3)	(2)	33	(18)
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 on derivative (effective portion)	(1)	0	1	1
Gain (loss) recognized in income on derivative (ineffective portion and amount excluded from effectiveness testing)	0	0	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 on derivative (effective portion)	(10)	12	22	(17)
Gain (loss) recognized in income on derivative (ineffective portion and amount excluded from effectiveness testing)	0	0	0	0
Cash Flow Hedges [Member] | Commodity Contracts [Member] | Discontinued Operations [Member]
Amounts Included in Income, OCI or Regulatory Liabilities/Assets [Abstract]
Gain (loss) reclassified from AOCI into income on derivative (effective portion)	0	8	13	30
Gain (loss) recognized in income on derivative (ineffective portion and amount excluded from effectiveness testing)	0	0	7	0
Net Investment Hedges [Member] | Foreign Currency Contracts [Member] | Other Comprehensive Income [Member]
Amounts Included in Income, OCI or Regulatory Liabilities/Assets [Abstract]
Gain (loss) recognized in OCI on derivative (effective portion)	7	25	6	7
Derivatives 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	(42)	(4)	(22)	(4)
Derivatives Designated As Hedging Instruments [Member] | Interest Rate Swaps [Member] | Regulatory Liabilities Noncurrent [Member]
Amounts Included in Income, OCI or Regulatory Liabilities/Assets [Abstract]
Gain (loss) recognized as regulatory liabilities/assets		6		6
Derivatives Designated As Hedging Instruments [Member] | Cash Flow Hedges [Member] | Interest Rate Swaps [Member] | Discontinued Operations [Member]
Amounts Included in Income, OCI or Regulatory Liabilities/Assets [Abstract]
Gain (loss) reclassified from AOCI into income on derivative (effective portion)	0		0
Gain (loss) recognized in income on derivative (ineffective portion and amount excluded from effectiveness testing)	0		(77)
Derivatives Not Designated As Hedging Instruments [Member]
Amounts Included in Income, OCI or Regulatory Liabilities/Assets [Abstract]
Gain (loss) recognized in income on derivative	76	132	58	32
Derivatives 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	(5)	0	(2)	(6)
Derivatives 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	(2)	(2)	(6)	(6)
Derivatives 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	78	134	64	38
LG And E And KU Energy LLC [Member] | Derivatives Designated As Hedging Instruments [Member] | Cash Flow Hedges [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	(42)	(4)	(22)	(4)
LG And E And KU Energy LLC [Member] | Derivatives Designated As Hedging Instruments [Member] | Cash Flow Hedges [Member] | Interest Rate Swaps [Member] | Regulatory Liabilities Noncurrent [Member]
Amounts Included in Income, OCI or Regulatory Liabilities/Assets [Abstract]
Gain (loss) recognized as regulatory liabilities/assets		6		6
LG And E And KU Energy LLC [Member] | Derivatives 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	(5)	0	(2)	(6)
LG And E And KU Energy LLC [Member] | Derivatives 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	(2)	(2)	(6)	(6)
Louisville Gas And Electric Co [Member] | Derivatives Designated As Hedging Instruments [Member] | Cash Flow Hedges [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	(21)	(2)	(11)	(2)
Louisville Gas And Electric Co [Member] | Derivatives Designated As Hedging Instruments [Member] | Cash Flow Hedges [Member] | Interest Rate Swaps [Member] | Regulatory Liabilities Noncurrent [Member]
Amounts Included in Income, OCI or Regulatory Liabilities/Assets [Abstract]
Gain (loss) recognized as regulatory liabilities/assets		3		3
Louisville Gas And Electric Co [Member] | Derivatives 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	(5)	0	(2)	(6)
Louisville Gas And Electric Co [Member] | Derivatives 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	(2)	(2)	(6)	(6)
Kentucky Utilities Co [Member] | Derivatives Designated As Hedging Instruments [Member] | Cash Flow Hedges [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	$ (21)	(2)	$ (11)	(2)
Kentucky Utilities Co [Member] | Derivatives Designated As Hedging Instruments [Member] | Cash Flow Hedges [Member] | Interest Rate Swaps [Member] | Regulatory Liabilities Noncurrent [Member]
Amounts Included in Income, OCI or Regulatory Liabilities/Assets [Abstract]
Gain (loss) recognized as regulatory liabilities/assets		$ 3		$ 3