Derivative Instruments and Hedging Activities (Risk Disclosures) (Details)	3 Months Ended					3 Months Ended				3 Months Ended				3 Months Ended
	Mar. 31, 2013 USD ($)	Mar. 31, 2012 USD ($)	Mar. 31, 2013 GBP (£)	Dec. 31, 2012 USD ($)	Dec. 31, 2012 GBP (£)	Mar. 31, 2013 WPD [Member] USD ($)	Mar. 31, 2013 WPD [Member] GBP (£)	Mar. 31, 2013 LG And E And KU Energy LLC [Member] USD ($)	Dec. 31, 2012 LG And E And KU Energy LLC [Member] USD ($)	Mar. 31, 2013 LG And E And KU Energy LLC [Member] LGE [Member] USD ($)	Mar. 31, 2013 LG And E And KU Energy LLC [Member] KU [Member] USD ($)	Mar. 31, 2013 Louisville Gas And Electric Co [Member] USD ($)	Dec. 31, 2012 Louisville Gas And Electric Co [Member] USD ($)	Mar. 31, 2013 Kentucky Utilities Co [Member] USD ($)
Interest Rate Risk - Cash Flow Hedges (Numeric) [Abstract]
Year of expiration of the maximum maturity date of interest rate cash flow hedge contracts	2043					2024	2024			2043	2043	2043		2043
Notional value of interest rate cash flow hedge contracts (excludes cross-currency contracts)	$ 1,100,000,000					$ 448,000,000	£ 295,000,000			$ 150,000,000	$ 150,000,000	$ 150,000,000		$ 150,000,000
Net notional value of cross-currency cash flow hedge contracts	1,300,000,000
Latest maturity date of cross-currency cash flow hedge contracts	2028
Insignificant or no hedge ineffectiveness associated with interest rate cash flow hedges	insignificant									no hedge ineffectiveness	no hedge ineffectiveness	no hedge ineffectiveness		no hedge ineffectiveness
No or insignificant after-tax gains (losses) previously recorded in AOCI reclassified to earnings related to interest rate cash flow hedge contracts	no such reclassifications	no such reclassifications
Net unrealized after-tax gains (losses) on interest rate cash flow hedge contracts expected to be reclassified into earnings during next 12 months	(11,000,000)
Interest Rate Risk - Fair Value Hedges (Numeric) [Abstract]
Year of expiration of the maximum maturity date of interest rate fair value hedge contracts		2047
Notional value of interest rate fair value hedges		99,000,000
No or insignificant hedge ineffectiveness associated with interest rate fair value hedges	did not recognize	did not recognize
No or insignificant gains (losses) associated with interest rate fair value hedges being excluded from the assessment of hedge effectiveness	did not recognize	did not recognize
No or insignificant gain (loss) associated with interest rate fair value hedges of debt issuances that no longer qualified as interest rate fair value hedges	did not recognize	did not recognize
Interest Rate Risk - Economic Activity (Numeric) [Abstract]
Notional amount of interest rate swaps classified as economic activity	179,000,000							179,000,000				179,000,000
Year of expiration of the maximum maturity date of interest rate economic activity contracts	2033							2033				2033
The fair value, net (asset) or liability, of interest rate swap contracts classified as economic activity	54,000,000			58,000,000				54,000,000	58,000,000			54,000,000	58,000,000
Foreign Currency Risk - Net Investment Hedges (Numeric) [Abstract]
Notional amount of net investment hedge contracts	261,000,000		162,000,000
Earliest settlement date of net investment hedge contracts	May 2013
Latest settlement date of net investment hedge contracts	December 2013
Fair value of net asset or (liability) position of net investment hedge contracts	15,000,000			(2,000,000)
Notional amount outstanding on intercompany loan qualified as a net investment hedge	69,000,000		46,000,000
Net after tax gains (losses) on net investment hedges recognized in the foreign currency translation adjustment component of AOCI	11,000,000
Insignificant or no net after tax gains (losses) on net investment hedges recognized in the foreign currency translation adjustment component of AOCI		insignificant
Net after tax gains (losses) on net investment hedges included in the foreign currency translation adjustment component of AOCI	25,000,000			14,000,000
Foreign Currency Risk - Economic Activity (Numeric) [Abstract]
Total exposure hedged related to foreign currency contracts for anticipated earnings hedges classified as economic activity	1,900,000,000		1,200,000,000	2,000,000,000	1,300,000,000
Fair value of net asset or (liability) position of foreign currency contracts for anticipated earnings hedges classified as economic activity	78,000,000			(42,000,000)
Earliest termination date of foreign currency contracts for anticipated earnings hedges classified as economic activity	April 2013
Latest termination date of foreign currency contracts for anticipated earnings hedges classified as economic activity	May 2015
Gains (losses) on foreign currency contracts for anticipated earnings hedges classified as economic activity	$ 119,000,000	$ (18,000,000)