Equity - AOCI Changes Net of Tax Table (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax Beginning of Period			$ (96)
Other Comprehensive Income (Loss)	$ 8	$ 3	29	$ (2)
Accumulated Other Comprehensive Income (Loss), Net of Tax End of Period	(67)		(67)
Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax Beginning of Period			(96)	(99)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			4	(23)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	8	7	25	21
Other Comprehensive Income (Loss)			29	(2)
Accumulated Other Comprehensive Income (Loss), Net of Tax End of Period	$ (67)	$ (101)	$ (67)	$ (101)