Income Taxes - Reconciliation of Effective Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of Effective Income Tax Rate
Statutory U.S. tax rate	21.00%	35.00%	35.00%
State income taxes--net of federal benefit	1.00%	0.80%	0.90%
International income taxes - net	0.20%	(6.30%)	(2.70%)
Global Intangible Low Taxed Income (GILTI)	1.10%
Foreign Derived Intangible Income (FDII)	(1.30%)
U.S. TCJA enactment - net impacts	2.50%	10.10%
U.S. research and development credit	(1.50%)	(0.70%)	(0.50%)
Reserves for tax contingencies	1.20%	2.20%	0.20%
Domestic Manufacturer’s deduction		(1.80%)	(1.80%)
Employee share-based payments	(1.40%)	(3.20%)	(2.80%)
All other--net	0.60%	(0.60%)
Effective worldwide tax rate (as a percent)	23.40%	35.50%	28.30%