Basis of Presentation - Effect of Adoption of ASU 2014-09 on Statement of Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income	$ 483	$ 485	$ 1,491	$ 1,345
Other comprehensive income (loss):
Foreign currency translation adjustments	(66)	107	(313)	457
Derivative instrument adjustments, net of tax	(1)	(5)	7	(13)
Unrealized gain (loss) on available-for-sale securities, net of tax	0	1	0	(1)
Pension and postretirement adjustments, net of tax	0	0	0	0
Reclassification of losses, net of tax	2	4	18	5
Net other comprehensive (loss) income	(65)	107	(288)	448
Comprehensive income	$ 418	592	$ 1,203	1,793
As Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income		392		1,171
Other comprehensive income (loss):
Foreign currency translation adjustments		107		457
Derivative instrument adjustments, net of tax		(5)		(13)
Unrealized gain (loss) on available-for-sale securities, net of tax		1		(1)
Pension and postretirement adjustments, net of tax		0		0
Reclassification of losses, net of tax		4		5
Net other comprehensive (loss) income		107		448
Comprehensive income		499		1,619
Adjustment | Adoption of ASU 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income		93		174
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, net of tax		0		0
Net other comprehensive (loss) income		0		0
Comprehensive income		$ 93		$ 174