Income Taxes - Reconciliation of Income Tax Expense (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Computed income tax expense at statutory federal income tax rate of 35%		$ 36,522	$ 22,655	$ 13,277
State income taxes, net of federal benefit		1,160	292	1,713
Deemed mandatory repatriation state tax		1,206
Deemed mandatory repatriation federal tax, net of foreign tax credit		6,936
Decrease in tax expense	[1]	8,000
Foreign tax rate differential		(5,031)	(882)	(1,181)
U.S. tax on current year foreign earnings, net of foreign tax credits		(2,726)	(373)	(948)
Change in valuation allowance		(796)	1,230	(944)
Other adjustments, net		627	(1,672)	(1,424)
Income tax expense		$ 45,898	$ 21,250	$ 10,493
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Computed income tax expense at statutory federal income tax rate of 35%, tax rate		35.00%	35.00%	35.00%
State income taxes, net of federal benefit, tax rate		1.10%	0.50%	4.50%
Deemed mandatory repatriation state tax rate		1.20%
Deemed mandatory repatriation federal tax, net of foreign tax credit, tax rate		6.60%
Decrease in tax percentage	[1]	7.70%
Foreign tax differentials rate		(4.80%)	(1.40%)	(3.10%)
U.S. tax on current year foreign earnings, net of foreign tax credits, tax rate		(2.60%)	(0.60%)	(2.50%)
Change in valuation allowance, tax rate		(0.80%)	1.90%	(2.50%)
Other adjustments, net, tax rate		0.60%	(2.60%)	(3.70%)
Income tax expense		44.00%	32.80%	27.70%

[1] Includes $0.6 million increase to the valuation allowance related to the remeasurement of deferred taxes due to the reduction in U.S. tax rate.