Basis of Presentation - Effect of Adoption of ASU 2014-09 on Statement of Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income	$ 398	$ 371
Other comprehensive income (loss):
Foreign currency translation adjustments	152	188
Derivative instrument adjustments, net of tax	(3)	(2)
Unrealized gain (loss) on available-for-sale securities, net of tax	0	(1)
Pension and postretirement adjustments, net of tax	0	0
Reclassification of losses (gains), net of tax	13	0
Net other comprehensive income (loss)	162	185
Comprehensive income	$ 560	556
As Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income		365
Other comprehensive income (loss):
Foreign currency translation adjustments		188
Derivative instrument adjustments, net of tax		(2)
Unrealized gain (loss) on available-for-sale securities, net of tax		(1)
Pension and postretirement adjustments, net of tax		0
Reclassification of losses (gains), net of tax		0
Net other comprehensive income (loss)		185
Comprehensive income		550
Adoption of ASU 2014-09 | Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income		6
Other comprehensive income (loss):
Foreign currency translation adjustments		0
Derivative instrument adjustments, net of tax		0
Unrealized gain (loss) on available-for-sale securities, net of tax		0
Pension and postretirement adjustments, net of tax		0
Reclassification of losses (gains), net of tax		0
Net other comprehensive income (loss)		0
Comprehensive income		$ 6