CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Statement [Abstract]
Net sales	$ 150,491	$ 153,133	$ 301,033	$ 304,911
Cost of sales	105,829	115,058	209,972	223,895
Gross profit	44,662	38,075	91,061	81,016
Research and development expenses	7,676	7,385	15,618	15,283
Selling, general and administrative expenses	27,965	24,230	57,811	51,227
Operating income	9,021	6,460	17,632	14,506
Interest income (expense), net	(127)	(372)	(235)	(1,004)
Accrued social insurance adjustment	0	9,464	0	9,464
Other income (expense), net	(17)	731	6	383
Income before provision for income taxes	8,877	16,283	17,403	23,349
Provision for income taxes	3,284	1,883	4,817	3,103
Net income	$ 5,593	$ 14,400	$ 12,586	$ 20,246
Earnings per share:
Basic (in dollars per share)	$ 0.41	$ 1.03	$ 0.92	$ 1.45
Diluted (in dollars per share)	$ 0.40	$ 1.02	$ 0.89	$ 1.43
Shares used in computing earnings per share:
Basic (in shares)	13,672	13,915	13,737	13,938
Diluted (in shares)	13,926	14,151	14,062	14,181