Summary of Allocation of Share Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense	$ 15,306	$ 13,436	$ 11,033
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense	4,978	4,153	3,362
Share-based compensation expense, net of tax	10,328	9,283	7,671
Cost of Sales
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense	1,031	1,579	1,317
Engineering, Research and Development Expense
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense	1,457	1,124	1,000
Selling, General And Administrative Expenses
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense	$ 12,818	$ 10,733	$ 8,716