Quarterly Financial Information (Unaudited) - Quarterly Financial Results (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 209,938	$ 197,886	$ 186,413	$ 191,660	$ 178,030	$ 180,041	$ 174,879	$ 165,487	$ 785,897	$ 698,437	$ 566,852
Gross profit	41,872	35,139	36,127	39,507	39,480	40,054	43,327	40,498	152,645	163,359	138,804
Net income	$ 7,184	$ 6,256	$ 10,450	$ 11,054	$ 13,848	$ 10,675	$ 13,125	$ 11,669	$ 34,944	$ 49,317	$ 37,187
Earnings per common share:
Basic (USD per share)	$ 0.42	$ 0.36	$ 0.61	$ 0.64	$ 0.81	$ 0.63	$ 0.77	$ 0.69	$ 2.03	$ 2.89	$ 2.20
Diluted (USD per share)	$ 0.42	$ 0.36	$ 0.60	$ 0.64	$ 0.80	$ 0.62	$ 0.76	$ 0.68	$ 2.02	$ 2.85	$ 2.16