Acquisitions and Dispositions (Narrative) (Details) - USD ($) $ in Millions	1 Months Ended	6 Months Ended
	Jul. 31, 2015	Jun. 30, 2015	Jun. 30, 2014	Apr. 02, 2015
Significant Acquisitions and Disposals [Abstract]
Payments to acquire businesses		$ 29	$ 16
Duke Energy Progress [Member] | NCEMPA Generating Assets [Member] | Subsequent Event [Member]
Significant Acquisitions and Disposals [Abstract]
Payments to acquire businesses	$ 1,250
Purchase acquisition adjustment	$ 350
Duke Energy Ohio [Member] | Midwest Generation Business [Member]
Discontinued Operations and Disposal Groups [Abstract]
Disposal Group, Including Discontinued Operation, Consideration				$ 2,800