Income Taxes - Reconciliation of the Difference between the Actual Provisions for Income Taxes (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Statutory federal income tax rate	35.00%	35.00%	35.00%
State income taxes	1.60%	2.10%	2.90%
Valuation allowances for deferred tax assets, including state	0.10%	1.30%	1.30%
Research and development credits	(1.00%)	(1.20%)	(1.50%)
Capitalized transaction costs	0.00%	0.70%	0.00%
Domestic production activities deduction	(1.80%)	(2.70%)	(1.60%)
Stock based compensation	(4.40%)	(2.10%)	(0.20%)
German Cartel settlement	0.00%	2.20%	0.00%
Foreign operations and intercompany financing	(2.80%)	(3.50%)	(1.30%)
Reserves for uncertain tax positions	(1.70%)	(0.10%)	(0.40%)
Repatriation of foreign undistributed earnings	1.30%	0.00%	0.00%
Revaluation of deferred tax liabilities due to federal rate change	(7.30%)	0.00%	0.00%
Other	0.50%	0.70%	0.70%
Effective income tax rate	19.50%	32.40%	34.90%