Derivative Instrument and Hedging Activities - Income Stmt (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Derivative [Line Items]
Gain Loss Recognized In Other Comprehensive Income Interest Rate Hedges	$ 0	$ 0	$ 0
Gain Loss Recognized in Interest Expense	0	0	(7)
Gain Loss Recognized In Distribution Commodity Contracts	$ 0	$ 0	$ 0