Derivative Instruments - Change in Unrealized Gains (Losses) in AOCI (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	$ 701	$ 243	$ 539
Other comprehensive income before reclassifications	122
Reclassifications from accumulated other comprehensive loss to net earnings	2
Ending Balance	768	701	243
Accumulated net gain (loss) from cash flow hedges attributable to parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	2	(1)	(1)
Other comprehensive income before reclassifications	9	7	0
Reclassifications from accumulated other comprehensive loss to net earnings	(9)	(4)	0
Ending Balance	$ 2	$ 2	$ (1)