Commitments and Contingencies (Environmental Matter and Other) (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2012 PartsPerBillion Gallons Pounds Integer MW	Dec. 31, 2011 Integer	Dec. 31, 2010 Integer	Apr. 30, 2012
Environmental Matters - Domestic - Air (Numeric) [Abstract]
Period over which capital expenditures are projected (in years)	5
Projected costs to comply with air matters for regulated subsidiaries	$ 3,100,000,000
Projected costs to comply with air matters for unregulated subsidiary	130,000,000
Environmental Matters - Domestic - Air - Mercury and Other Hazardous Air Pollutants (Numeric) [Abstract]
Period for compliance with final MACT standards (in years)	3
Possible period of extension to comply with final MACT standards (in years)	1
Environmental Matters - Domestic - Air - Greenhouse Gas Regulations and Tort Litigation (Numeric) [Abstract]
Number of northeastern states that signed a Memorandum of Understanding that established RGGI	10
Minimum capacity of electric power plants that are impacted by RGGI's emissions stabilization program (in MW)	25
Percentage reduction by 2019 in carbon dioxide emissions under RGGI	10.00%
Maximum percentage reduction in greenhouse gas emissions by implementing actions identified in a Pennsylvania 2009 report	30.00%
Proposed mandatory percentage improvement at power plants	5.00%
Number of western states that are members of the WCI	11
WCI's target percentage for reducing carbon dioxide emissions	15.00%
Number of electric utility companies affected by a September 2009 U.S. Court of Appeals for the Second Circuit decision	5
Number of companies cited in May 2011 Mississippi court filing	87
Carbon dioxide emitted from PPL power plants during the reporting period (in millions of tons)		74	68
Number of pounds in a ton of carbon dioxide emissions	2,000
Environmental Matters - Domestic - Air - Renewable Energy Legislation (Numeric) [Abstract]
Minimum percentage of renewable energy supply and energy efficiency required by 2020	15.00%
Maximum percentage of renewable energy supply and energy efficiency required by 2020	20.00%
Environmental Matters - Domestic - Water/Waste - Coal Combustion Residuals (Numeric) [Abstract]
Number of approaches proposed by EPA in June 2010 to regulate CCRs	2
Environmental Matters - Domestic - Water/Waste - Martins Creek Fly Ash Release (Numeric) [Abstract]
Gallons of water released at the Martins Creek plant in 2005 that contained fly ash	100,000,000
Number of coal-fired generating units at the Martins Creek plant at the time of fly ash release	2
Capacity of each coal-fired generating unit at the Martins Creek plant (in MW)	150
Amounts incurred through period end for remediation and related costs related to 2005 Martins Creek fly ash release	28,000,000
Environmental Matters - Domestic - Water/Waste - Seepages and Groundwater Infiltration - Pennsylvania, Montana and Kentucky (Numeric) [Abstract]
Number of plaintiffs that filed a lawsuit against the Colstrip plant owners in 2007 for seepage issues	6
Period to complete a settlement (in days)	60
Environmental Matters - Domestic - Water/Waste - Clean Water Act 316(b) (Numeric) [Abstract]
Number of requirements under proposed EPA rule regarding reducing impact to aquatic organisms	2
Number of factors to make a site-specific determination	9
Environmental Matters - Domestic - Water/Waste - Other Issues (Numeric) [Abstract]
EPA's current drinking water standard relating to arsenic (in parts per billion)	10
Increase in cancer risk related to arsenic in drinking water	20 times
The EPA's proposed drinking water standard relating to arsenic (in parts per billion)	0.1
Number of alternatives provided to the DEP to address fish kill issues at Brunner Island	3
Other - Nuclear Insurance (Numeric) [Abstract]
Maximum amount of insured property damage losses at nuclear station	2,750,000,000
Maximum assessment for retroactive premiums for nuclear outage insurance coverage	44,000,000			48,000,000
Maximum public liability for claims resulting an incident at nuclear station	12,600,000,000
Maximum amount that could be assessed resulting from an incident at nuclear station	235,000,000
Maximum amount payable per year resulting from an incident at nuclear station	$ 35,000,000