Income Taxes - Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of income tax expense computed at the federal statutory rate to the provision for income taxes
Federal income tax expense at statutory rate	$ 22,294	$ 23,192	$ 21,699
State taxes, net of federal benefit	2,547	1,077	1,694
Valuation allowance changes	(7)	(1,028)
Change in uncertain tax positions, net	50	43	8
Research and development credit	(274)	(241)	(249)
Rate change	64	(30)	366
Manufacturing tax benefits	(1,248)	(1,302)	(1,612)
Prior period adjustments	1,096
Other	165	376	130
Provision for income tax expense (benefit)	$ 24,687	$ 22,087	$ 22,036