Acquisitions and Dispositions (Plants in Disposal Group) (Details) - Mar. 31, 2015 - Duke Energy Ohio [Member] - MW	Total
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total Average MW Capacity	9,225
Owned Average MW Capacity	5,884
Stuart [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total Average MW Capacity	2,308
Owned Average MW Capacity	900
Ownership Interest	39.00%
Zimmer [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total Average MW Capacity	1,300
Owned Average MW Capacity	605
Ownership Interest	46.50%
Hanging Rock [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total Average MW Capacity	1,226
Owned Average MW Capacity	1,226
Ownership Interest	100.00%
Miami Fort Units 7 and 8 [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total Average MW Capacity	1,020
Owned Average MW Capacity	652
Ownership Interest	64.00%
Conesville [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total Average MW Capacity	780
Owned Average MW Capacity	312
Ownership Interest	40.00%
Washington [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total Average MW Capacity	617
Owned Average MW Capacity	617
Ownership Interest	100.00%
Fayette [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total Average MW Capacity	614
Owned Average MW Capacity	614
Ownership Interest	100.00%
Killen [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total Average MW Capacity	600
Owned Average MW Capacity	198
Ownership Interest	33.00%
Lee [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total Average MW Capacity	568
Owned Average MW Capacity	568
Ownership Interest	100.00%
Dicks Creek [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total Average MW Capacity	136
Owned Average MW Capacity	136
Ownership Interest	100.00%
Miami Fort [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total Average MW Capacity	56
Owned Average MW Capacity	56
Ownership Interest	100.00%