Acquisitions and Dispositions - Dispositions (Narrative) (Details) $ in Millions		12 Months Ended
	Apr. 02, 2015 USD ($) MW	Dec. 31, 2016 USD ($) MW	Dec. 31, 2017 USD ($)
International Energy [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from Divestiture of Businesses		$ 1,900
DEI Latin American [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Owned Plant Capacity | MW		2,230
Enterprise Value		$ 1,200
DEI Brazil Holdings [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Owned Plant Capacity | MW		2,090
Enterprise Value		$ 1,200
Duke Energy Ohio [Member] | Midwest Generation Business [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Owned Plant Capacity | MW	5,900
Proceeds from Divestiture of Businesses, Net of Cash Divested	$ 2,800
Obligations [Member] | International Energy [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Tax obligations			$ 78