Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule of Quarterly Financial Information Disclosure [Line Items]
Sales	$ 224,431	$ 231,614	$ 215,734	$ 207,798	$ 223,911	$ 234,783	$ 207,751	$ 172,610
Gross profit	48,737	57,509	50,665	45,537	48,372	55,440	47,286	38,130	$ 202,448	$ 189,228	$ 158,510
Net income	$ 11,384	$ 14,756	$ 9,710	$ 7,359	$ 11,351	$ 13,367	$ 9,195	$ 7,238	$ 43,209	$ 41,151	$ 36,094
Per common share - diluted
Diluted (in dollars per share)	$ 0.99	$ 1.28	$ 0.84	$ 0.64	$ 1.00	$ 1.10	$ 0.75	$ 0.59	$ 3.76	$ 3.42	$ 2.96
Average shares
Diluted (in shares)	11,500	11,496	11,498	11,436	11,403	12,205	12,276	12,270	11,482	12,039	12,212
Dividends per share (in dollars per share)	$ 0.08	$ 0.08	$ 0.08	$ 0.08	$ 0.07	$ 0.07	$ 0.07	$ 0.07
High
Market price of common stock
Share Price (in dollars per share)	57.51	55.12	64.45	63.39	52.13	55.84	57.86	60.65	$ 57.51	$ 52.13
Low
Market price of common stock
Share Price (in dollars per share)	$ 43.98	$ 44.48	$ 48.1	$ 44.74	$ 37.93	$ 40.75	$ 49.50	$ 46.87	$ 43.98	$ 37.93