Equity - AOCI Changes Net of Tax Table (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 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)	$ 7	$ (5)	21	$ (5)
Accumulated Other Comprehensive Income (Loss), Net of Tax End of Period	(75)		(75)
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	(19)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			17	14
Other Comprehensive Income (Loss)			21	(5)
Accumulated Other Comprehensive Income (Loss), Net of Tax End of Period	$ (75)	$ (104)	$ (75)	$ (104)