Equity - Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	$ 388	$ 65	$ 684	$ 768
Balance at end of period	570	633	570	633
Pension and other postretirement benefit plans, tax (less than)	0	(4)	28	(3)
Accumulated Other Comprehensive Loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(633)	(630)	(742)	(649)
Other comprehensive income before reclassifications			6
Reclassifications from accumulated other comprehensive loss to net earnings			85
Net other comprehensive income			91
Balance at end of period	(651)	$ (705)	(651)	$ (705)
Foreign Currency Translation Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period			(339)
Other comprehensive income before reclassifications			5
Reclassifications from accumulated other comprehensive loss to net earnings			0
Net other comprehensive income			5
Balance at end of period	(334)		(334)
Pension and Postretirement Benefit Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period			(407)
Other comprehensive income before reclassifications			(3)
Reclassifications from accumulated other comprehensive loss to net earnings			89
Net other comprehensive income			86
Balance at end of period	(321)		(321)
Pension and other postretirement benefit plans, tax (less than)			28
Unrealized Gain (Loss) on Foreign Forward Exchange Contracts
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period			4
Other comprehensive income before reclassifications			4
Reclassifications from accumulated other comprehensive loss to net earnings			(4)
Net other comprehensive income			0
Balance at end of period	$ 4		$ 4