Income Taxes (Details) - Differences Between U.S. Federal Statutory Income Tax Rate and Effective Tax Rate on Income Before Income Taxes	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Statutory tax rate	35.00%	35.00%	35.00%
State income taxes, net of federal benefit	3.60%	2.40%	3.50%
Effect of non-U.S. operations	5.90%	(6.10%)	(6.90%)
Record (release) reserve for tax contingencies	(2.80%)	3.20%	1.70%
Law changes	0.418	0.000	(0.002)
Excess tax benefits from stock based compensation	11.00%	(3.80%)	(0.00%)
Nondeductible acquisition costs	(7.90%)	2.60%	0.80%
Nondeductible meals and entertainment costs	(3.50%)	1.10%	1.10%
Capital loss	13.10%	0.00%	0.00%
Record (release) valuation allowance	3.00%	(0.20%)	0.50%
Other items, net	3.40%	(1.30%)	0.00%
Effective tax rate	102.60%	32.90%	35.50%