Stock-Based Compensation - Stock-based Compensation Expense and Related Income Tax Benefit (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Employee and director stock-based compensation expense	$ 2,204	$ 2,623
Income tax benefit	463	815
Cost of sales
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Employee and director stock-based compensation expense	17	15
Research and development expenses
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Employee and director stock-based compensation expense	155	119
Selling, general and administrative expenses | Employees
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Employee and director stock-based compensation expense	1,528	1,744
Selling, general and administrative expenses | Outside directors
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Employee and director stock-based compensation expense	$ 504	$ 745