Income Taxes - Effective Rate Differences (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Differences between the U.S. federal statutory tax rate and the effective income tax rate
U.S. federal statutory rate (as a percent)	35.00%	35.00%	35.00%
State income taxes, net of federal income tax benefit (as a percent)	2.90%	1.80%	2.20%
Tax rate differential on foreign income (as a percent)	(6.50%)	(3.10%)	(2.90%)
Permanent tax differences (as a percent)	3.20%		0.30%
Permanent tax differences (as a percent)		(1.60%)
Valuation allowance (as a percent)	0.80%	0.30%
Settlement of uncertain tax positions (as a percent)			(1.90%)
Tax statute expiration (as a percent)	(0.30%)	(0.60%)	(0.60%)
Change in uncertain tax positions (as a percent)	0.40%	0.10%	0.10%
Deferred tax benefit for Section 987	(2.70%)
Other - net (as a percent)	(1.50%)	(0.50%)	(0.30%)
Effective income tax rate (as a percent)	31.30%	31.40%	31.90%