Summary of Unaudited Quarterly Results of Operations Summary of Unaudited Quarterly Results of Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 80,633	$ 75,651	$ 75,006	$ 74,617	$ 67,315	$ 70,199	$ 69,348	$ 69,711	$ 305,907	$ 276,573	$ 275,834
Gross profit	46,993	46,005	45,141	44,879	40,504	42,573	42,526	42,459	183,018	168,062	169,124
Net income (loss)	$ 20,237	$ 1,321	$ 7,273	$ 857	$ (4,643)	$ 1,825	$ 172	$ 1,017	$ 29,688	$ (1,629)	$ 297
Earnings Per Share, Basic	$ 2.28	$ 0.15	$ 0.82	$ 0.10	$ (0.53)	$ 0.21	$ 0.02	$ 0.12	$ 3.35	$ (0.19)	$ 0.03
Earnings Per Share, Diluted	$ 2.21	$ 0.14	$ 0.80	$ 0.09	$ (0.53)	$ 0.20	$ 0.02	$ 0.11	$ 3.25	$ (0.19)	$ 0.03