Fair Value Measurements (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Liabilities [Abstract]
Contingent consideration	$ 31	$ 20	$ 31
Business Combination, Contingent Consideration, Liability [Abstract]
Balance at beginning of period	31
Acquisitions and investments	11
Cash payments	(7)
Changes in fair value of contingent consideration, net	(15)
Balance at end of period	20
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Assets [Abstract]
Cash equivalents		660	310
Derivatives (foreign currency forward contracts)		0	0
Total assets		660	310
Liabilities [Abstract]
Derivatives (foreign currency forward contracts)		0	0
Contingent consideration	0	0	0
Total liabilities		0	0
Business Combination, Contingent Consideration, Liability [Abstract]
Balance at beginning of period	0
Balance at end of period	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Assets [Abstract]
Cash equivalents		0	0
Derivatives (foreign currency forward contracts)		1	11
Total assets		1	11
Liabilities [Abstract]
Derivatives (foreign currency forward contracts)		17	1
Contingent consideration	0	0	0
Total liabilities		17	1
Business Combination, Contingent Consideration, Liability [Abstract]
Balance at beginning of period	0
Balance at end of period	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Assets [Abstract]
Cash equivalents		0	0
Derivatives (foreign currency forward contracts)		0	0
Total assets		0	0
Liabilities [Abstract]
Derivatives (foreign currency forward contracts)		0	0
Contingent consideration	31	20	31
Total liabilities		$ 20	$ 31
Business Combination, Contingent Consideration, Liability [Abstract]
Balance at beginning of period	31
Balance at end of period	$ 20