Unaudited: Quarterly Results of Operations, Common Stock Price and Dividends (Details) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2021 USD ($) Stockholder $ / shares	Sep. 30, 2021 USD ($) $ / shares	Jun. 30, 2021 USD ($) $ / shares	Mar. 31, 2021 USD ($) $ / shares	Dec. 31, 2020 USD ($) Stockholder $ / shares	Sep. 30, 2020 USD ($) $ / shares	Jun. 30, 2020 USD ($) $ / shares	Mar. 31, 2020 USD ($) $ / shares	Dec. 31, 2021 USD ($) Stockholder $ / shares	Dec. 31, 2020 USD ($) Stockholder $ / shares	Dec. 31, 2019 USD ($) $ / shares
Number of shareholders | Stockholder	557				656				557	656
Net sales | $	$ 135,748	$ 128,738	$ 122,869	$ 117,842	$ 112,329	$ 113,587	$ 91,119	$ 108,508	$ 505,198	$ 425,544	$ 424,625
Gross margin | $	54,835	51,184	50,102	49,362	44,055	45,023	35,850	43,322	205,484	168,249	163,528
Net earnings | $	$ 17,276	$ 15,855	$ 13,972	$ 13,781	$ 13,094	$ 14,861	$ 9,534	$ 11,854	$ 60,884	$ 49,343	$ 47,177
Earnings per share:
Basic	$ 0.59	$ 0.54	$ 0.48	$ 0.47	$ 0.45	$ 0.51	$ 0.33	$ 0.41	$ 2.09	$ 1.70	$ 1.63
Diluted	0.59	0.54	0.48	0.47	0.45	0.51	0.33	0.41	2.08	1.69	1.61
Dividends declared	0.20	0.20	0.18	0.18	0.18	0.18	0.17	0.17	0.76	0.70	$ 0.64
Stock price	105.64	101.14	98.12	93.07	94.06	65.37	62.92	53.60	105.64	94.06
High
Earnings per share:
Stock price	112.36	108.25	100.01	111.77	96.00	68.25	68.01	70.83	112.36	96.00
Low
Earnings per share:
Stock price	$ 99.13	$ 93.88	$ 89.29	$ 88.98	$ 64.96	$ 59.53	$ 47.00	$ 41.50	$ 99.13	$ 64.96