Dispositions Dispositions (Details) - USD ($) $ in Millions			3 Months Ended		6 Months Ended
	Jan. 27, 2016	Jan. 01, 2016	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from the sale of businesses, net of cash sold					$ 156	$ 2
Gain (Loss) on Disposition of Business			$ (17)	$ 0	30	0
Proceeds from sale of ownership interest					$ (134)	$ (461)
UK Wind Projects [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (Loss) on Disposition of Business			$ (20)
DPLER [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from the sale of businesses, net of cash sold		$ 76
Gain (Loss) on Disposition of Business		$ 49
Kelanitissa [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from the sale of businesses, net of cash sold	$ 18
Gain (Loss) on Disposition of Business	$ (5)