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Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Quarterly Financial Information Disclosure [Line Items]
Sales	$ 300,189	$ 271,829	$ 285,186	$ 261,934	$ 256,038	$ 257,572	$ 257,125	$ 238,087	$ 1,119,138	$ 1,008,822	$ 912,380
Gross profit	68,076	68,710	73,133	63,308	62,632	66,772	66,454	60,257	273,227	256,115	234,693
Net income	$ 9,568	$ 17,418	$ 20,667	$ 15,253	$ 16,589	$ 23,543	$ 18,771	$ 14,583	$ 62,906	$ 73,486	$ 44,315
Earnings per share
Diluted (in dollars per share)	$ 0.81	$ 1.47	$ 1.75	$ 1.30	$ 1.41	$ 2.00	$ 1.60	$ 1.24	$ 5.33	$ 6.25	$ 3.79
Average shares
Diluted (in shares)	11,811	11,813	11,798	11,777	11,768	11,777	11,759	11,739	11,800	11,761	11,682
Dividends per share (in dollars per share)	$ 0.12	$ 0.12	$ 0.12	$ 0.12	$ 0.11	$ 0.11	$ 0.11	$ 0.11
High
Market price of common stock
Share Price (in dollars per share)	129.74	124.33	106.19	101.58	93.45	102.29	118.93	120.22	$ 129.74	$ 93.45
Low
Market price of common stock
Share Price (in dollars per share)	$ 103.60	$ 93.11	$ 93.00	$ 74.74	$ 72.85	$ 88.13	$ 88.60	$ 103.38	$ 103.60	$ 72.85

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