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Summary of Significant Accounting Policies Equity Method Investment (Details) (Transource Energy, LLC [Member])
9 Months Ended
Sep. 30, 2014
Schedule of Equity Method Investments [Line Items]  
Equity Method Investment, Description of Principal Activities Transource is focused on the development of competitive electric transmission projects.
GPE Transmission Holding Company, LLC [Member]
 
Schedule of Equity Method Investments [Line Items]  
Equity Method Investment, Ownership Percentage 13.50%
AEP Transmission Holding Company, LLC [Member]
 
Schedule of Equity Method Investments [Line Items]  
Ownership Percentage of Majority Owner 86.50%