Basis of Presentation - Effect of Adoption of ASU 2014-09 on Statement of Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income	$ 610	$ 489	$ 1,008	$ 860
Other comprehensive income (loss):
Foreign currency translation adjustments	(399)	162	(247)	350
Derivative instrument adjustments, net of tax	11	(6)	8	(8)
Unrealized gain (loss) on available-for-sale securities, net of tax	0	(1)	0	(2)
Pension and postretirement adjustments, net of tax	0	0	0	0
Reclassification of losses (gains), net of tax	3	1	16	1
Net other comprehensive (loss) income	(385)	156	(223)	341
Comprehensive income	$ 225	645	$ 785	1,201
As Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income		414		779
Other comprehensive income (loss):
Foreign currency translation adjustments		162		350
Derivative instrument adjustments, net of tax		(6)		(8)
Unrealized gain (loss) on available-for-sale securities, net of tax		(1)		(2)
Pension and postretirement adjustments, net of tax		0		0
Reclassification of losses (gains), net of tax		1		1
Net other comprehensive (loss) income		156		341
Comprehensive income		570		1,120
Adjustment | Adoption of ASU 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income		75		81
Other comprehensive income (loss):
Foreign currency translation adjustments		0		0
Derivative instrument adjustments, net of tax		0		0
Unrealized gain (loss) on available-for-sale securities, net of tax		0		0
Pension and postretirement adjustments, net of tax		0		0
Reclassification of losses (gains), net of tax		0		0
Net other comprehensive (loss) income		0		0
Comprehensive income		$ 75		$ 81