Derivative Instruments and Hedging Activities (Gains and Losses) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
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)	$ (91)	$ 112	$ 53
Gain (loss) recognized in income on derivative (ineffective portion and amount excluded from effectiveness testing)	0	0	(70)
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)	(98)	109	26
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)	0	(21)	(34)
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)	(9)	(7)	(11)
Gain (loss) recognized in income on derivative (ineffective portion and amount excluded from effectiveness testing)	0	0	0
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
Gain (loss) recognized in income on derivative (ineffective portion and amount excluded from effectiveness testing)			(77)
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)	(98)	130	60
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)	(82)	116	49
Gain (loss) recognized in income on derivative (ineffective portion and amount excluded from effectiveness testing)	0	0	0
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)		3	2
Gain (loss) recognized in income on derivative (ineffective portion and amount excluded from effectiveness testing)		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)			13
Gain (loss) recognized in income on derivative (ineffective portion and amount excluded from effectiveness testing)			7
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)	1	2	9
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	0	0	(22)
Derivatives Not Designated As Hedging Instruments [Member]
Amounts Included in Income, OCI or Regulatory Liabilities/Assets [Abstract]
Gain (loss) recognized in income on derivative	(267)	377	114
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	7	1
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	(6)	(7)	(8)
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	(261)	384	122
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	0	0	(22)
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	7	1
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	(6)	(7)	(8)
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	0	0	(11)
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	7	1
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	(6)	(7)	(8)
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	$ 0	$ 0	$ (11)

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- Definition

The amount of gain (loss) recognized as regulatory assets/liabilities during the period on derivative instruments designated as hedging instruments and not designated as hedging instruments for which regulatory treatment is being applied.

+ References

No definition available.

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- Definition

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5618551-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (a),(c),(d),(e)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

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- Definition

The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4D
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624177-113959

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- Definition

The portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments representing (a) the amount of the hedge ineffectiveness and (b) the amount, if any, excluded from the assessment of hedge effectiveness.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 25
-Section 50
-Paragraph 1
-Subparagraph (a)(1),(2)
-URI http://asc.fasb.org/extlink&oid=6886632&loc=d3e76258-113986

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- Definition

The effective portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments that was recognized in other comprehensive income during the current period.

+ References

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