Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule of Quarterly Financial Information Disclosure [Line Items]
Sales	$ 205,522	$ 216,766	$ 211,489	$ 210,971	$ 224,431	$ 231,614	$ 215,734	$ 207,798
Gross profit	47,933	54,711	52,178	50,277	48,737	57,509	50,665	45,537	$ 205,099	$ 202,448	$ 189,228
Net income	$ 7,588	$ 13,236	$ 10,562	$ 8,659	$ 11,384	$ 14,756	$ 9,710	$ 7,359	$ 40,045	$ 43,209	$ 41,151
Per common share - diluted
Diluted (in dollars per share)	$ 0.65	$ 1.14	$ 0.92	$ 0.75	$ 0.99	$ 1.28	$ 0.84	$ 0.64	$ 3.46	$ 3.76	$ 3.42
Average shares
Diluted (in shares)	11,608	11,595	11,550	11,507	11,500	11,496	11,498	11,436	11,565	11,482	12,039
Dividends per share (in dollars per share)	$ 0.09	$ 0.09	$ 0.09	$ 0.09	$ 0.08	$ 0.08	$ 0.08	$ 0.08
High
Market price of common stock
Share Price (in dollars per share)	78.91	68.04	66.01	61.82	57.51	55.12	64.45	63.39	$ 78.91	$ 57.51
Low
Market price of common stock
Share Price (in dollars per share)	$ 59.55	$ 61.49	$ 52.82	$ 48.26	$ 43.98	$ 44.48	$ 48.1	$ 44.74	$ 59.55	$ 43.98