Stock-Based Compensation - Stock-based Compensation Expense and Related Income Tax Benefit (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Employee and director stock-based compensation expense	$ 2,527	$ 2,139	$ 6,718	$ 6,808
Income tax benefit	509	441	1,385	1,423
Cost of sales
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Employee and director stock-based compensation expense	37	21	102	61
Research and development expenses
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Employee and director stock-based compensation expense	315	200	809	556
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	1,866	1,671	5,005	4,936
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	$ 309	$ 247	$ 802	$ 1,255