Utility Rate Regulation (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012 MW Integer		Dec. 31, 2011
Regulatory Assets [Line Items]
Current regulatory assets	$ 15		$ 9
Noncurrent regulatory assets	1,334		1,349
Regulatory Liabilities [Line Items]
Current regulatory liabilities	74		73
Noncurrent regulatory liabilities	1,009		1,010
Regulatory Matters - Kentucky Activities - Certificate of Public Convenience and Necessity Filing (Numeric) [Abstract]
Capacity of proposed NGCC (in MW)	640
LG&E undivided ownership interest in proposed combined cycle turbine	22.00%
KU undivided ownership interest in proposed combined cycle turbine	78.00%
Capacity of turbines the company plans to purchase (in MW)	495
LG&E's undivided ownership interest in purchase of three turbines	69.00%
KU's undivided ownership interest in purchase of three turbines	31.00%
Generating units anticipated to be retired at the Cane Run plant	3
Generating units anticipated to be retired at the Tyrone plant	1
Generating units anticipated to be retired at the Green River plant	2
Capacity of coal-fired generation units that the company anticipates retiring in 2015 (in MW)	797
Combined cost of Bluegrass and NGCC	800
Regulatory Matters - Kentucky Activities - Kentucky Acquisition Commitments (Numeric) [Abstract]
Rate of return on common equity if exceeded triggers costs savings being returned to customers	10.75%
Regulatory Matters - Pennsylvania Activities - PUC Investigation of Retail Market (Numeric) [Abstract]
Number of phases of a PUC investigation of retail electricity market	2
Number of possible models for the default service end state	3
Regulatory Matters - Pennsylvania Activities - Legislation - Regulatory Procedures and Mechanisms (Numeric) [Abstract]
Number of ratemaking mechanisms authorized for PUC approval	2
Regulatory Matters - Federal Matters - FERC Formula Rates (Numeric) [Abstract]
Requested recovery period (in years)	34
Regulatory asset amount recorded related to certain deferred state tax assets	51		51
Regulatory Matters - U.K. Activities - Ofgem Review of Line Loss Calculation (Numeric) [Abstract]
WPD's projected cost for compliance with overhead electricity standards	173		170
Number of potential changes cited in a consultation paper issued by Ofgem	2
Generation Supply Charge [Member]
Regulatory Liabilities [Line Items]
Current regulatory liabilities	35		42
Environmental Cost Recovery [Member]
Regulatory Liabilities [Line Items]
Current regulatory liabilities	9		7
Gas Supply Clause [Member]
Regulatory Liabilities [Line Items]
Current regulatory liabilities	6		6
Transmission Service Charge [Member]
Regulatory Liabilities [Line Items]
Current regulatory liabilities	5		2
Transmission Formula Rate [Member]
Regulatory Liabilities [Line Items]
Current regulatory liabilities	7		0
Accumulated Cost Of Removal Of Utility Plant [Member]
Regulatory Liabilities [Line Items]
Noncurrent regulatory liabilities	658		651
Coal Contracts [Member]
Regulatory Liabilities [Line Items]
Noncurrent regulatory liabilities	170	[1]	180	[1]
Power Purchase Agreement OVEC [Member]
Regulatory Liabilities [Line Items]
Noncurrent regulatory liabilities	114	[1]	116	[1]
Net Deferred Tax Assets [Member]
Regulatory Liabilities [Line Items]
Noncurrent regulatory liabilities	38		39
Act 129 Compliance Rider [Member]
Regulatory Liabilities [Line Items]
Noncurrent regulatory liabilities	12		7
Defined Benefit Plans [Member]
Regulatory Liabilities [Line Items]
Noncurrent regulatory liabilities	9		9
Other Regulatory Liabilities [Member]
Regulatory Liabilities [Line Items]
Current regulatory liabilities	12		16
Noncurrent regulatory liabilities	8		8
Gas Supply Clause [Member]
Regulatory Assets [Line Items]
Current regulatory assets	7		6
Fuel Adjustment Clause [Member]
Regulatory Assets [Line Items]
Current regulatory assets	8		3
Defined Benefit Plans [Member]
Regulatory Assets [Line Items]
Noncurrent regulatory assets	605		615
Taxes Recoverable Through Future Rates [Member]
Regulatory Assets [Line Items]
Noncurrent regulatory assets	293		289
Storm Costs [Member]
Regulatory Assets [Line Items]
Noncurrent regulatory assets	149		154
Unamortized Loss On Debt [Member]
Regulatory Assets [Line Items]
Noncurrent regulatory assets	106		110
Interest Rate Swaps [Member]
Regulatory Assets [Line Items]
Noncurrent regulatory assets	62		69
Accumulated Cost Of Removal Of Utility Plant [Member]
Regulatory Assets [Line Items]
Noncurrent regulatory assets	59		53
Coal Contracts [Member]
Regulatory Assets [Line Items]
Noncurrent regulatory assets	9	[1]	11	[1]
Asset Retirement Obligations [Member]
Regulatory Assets [Line Items]
Noncurrent regulatory assets	21		18
Other Regulatory Assets [Member]
Regulatory Assets [Line Items]
Noncurrent regulatory assets	$ 30		$ 30

[1] These regulatory assets and liabilities were recorded as offsets to certain intangible assets and liabilities that were recorded at fair value upon the acquisition of LKE.