Basis of Presentation and Significant Accounting Policies - Condensed Statements of Operations, Pro Forma Amounts Under Previous Guidance (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net sales	$ 182,717	$ 175,652	$ 509,938	$ 514,638
Cost of sales	142,401	132,582	405,661	386,783
Selling, general and administrative expenses	29,994	32,997	90,811	94,701
Provision for income taxes	311	1,824	2,233	2,945
Net income	$ 959	$ 1,728	$ 23,031	$ 6,531
Earnings per share:
Basic (in dollars per share)	$ 0.07	$ 0.12	$ 1.65	$ 0.45
Diluted (in dollars per share)	$ 0.07	$ 0.12	$ 1.63	$ 0.44
Without Adoption of ASU 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net sales	$ 184,559		$ 512,880
Cost of sales	144,426		408,427
Selling, general and administrative expenses	30,029		90,866
Provision for income taxes	355		2,250
Net income	$ 697		$ 23,134
Earnings per share:
Basic (in dollars per share)	$ 0.05		$ 1.66
Diluted (in dollars per share)	$ 0.05		$ 1.64
Effect of Change | ASU 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net sales	$ (1,842)		$ (2,942)
Cost of sales	(2,025)		(2,766)
Selling, general and administrative expenses	(35)		(55)
Provision for income taxes	(44)		(17)
Net income	$ 262		$ (103)
Earnings per share:
Basic (in dollars per share)	$ 0.02		$ (0.01)
Diluted (in dollars per share)	$ 0.02		$ (0.01)