Other Income and Expense (Nonoperating Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Public Utilities, Allowance for Funds Used During Construction, Additions	$ 29	$ 17	$ 9
Gain (Loss) on Disposition of Other Assets	5	19	66
Gain (Loss) on Contract Termination	0	20	0
Contingency reversal	0	0	18
Other	31	26	28
Total other income	$ 65	$ 82	$ 121