Equity - Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Net unrealized gains on cash flow hedges, net of taxes, beginning of period	$ 711
Other comprehensive income before reclassifications	17
Reclassifications from accumulated other comprehensive loss to net earnings	2
Net other comprehensive income	19
Net unrealized gains on cash flow hedges, net of taxes, end of period	7
Pension and other postretirement benefit plans, tax	(1)	$ (1)
Accumulated Other Comprehensive Loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Net unrealized gains on cash flow hedges, net of taxes, beginning of period	(649)
Net unrealized gains on cash flow hedges, net of taxes, end of period	(630)
Foreign Currency Translation Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Net unrealized gains on cash flow hedges, net of taxes, beginning of period	(239)
Other comprehensive income before reclassifications	5
Reclassifications from accumulated other comprehensive loss to net earnings	0
Net other comprehensive income	5
Net unrealized gains on cash flow hedges, net of taxes, end of period	(234)
Pension and Postretirement Benefit Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Net unrealized gains on cash flow hedges, net of taxes, beginning of period	(402)
Other comprehensive income before reclassifications	0
Reclassifications from accumulated other comprehensive loss to net earnings	3
Net other comprehensive income	3
Net unrealized gains on cash flow hedges, net of taxes, end of period	(399)
Pension and other postretirement benefit plans, tax	1
Unrealized Gain (Loss) on Forward Exchange Contracts
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Net unrealized gains on cash flow hedges, net of taxes, beginning of period	2	2
Other comprehensive income before reclassifications	2
Reclassifications from accumulated other comprehensive loss to net earnings	(1)
Net other comprehensive income	1
Net unrealized gains on cash flow hedges, net of taxes, end of period	3	$ 7
Unrealized Gain (Loss) on Investments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Net unrealized gains on cash flow hedges, net of taxes, beginning of period	(10)
Other comprehensive income before reclassifications	10
Reclassifications from accumulated other comprehensive loss to net earnings	0
Net other comprehensive income	10
Net unrealized gains on cash flow hedges, net of taxes, end of period	$ 0