CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Net sales	$ 153,505	$ 200,724	$ 458,416	$ 578,783
Cost of sales	109,349	154,245	333,244	458,437
Gross profit	44,156	46,479	125,172	120,346
Research and development expenses	7,696	7,930	22,979	21,884
Selling, general and administrative expenses	26,214	32,422	77,441	94,598
Operating income	10,246	6,127	24,752	3,864
Interest income (expense), net	(268)	(784)	(1,272)	(3,088)
Accrued social insurance adjustment	0	0	9,464	0
Other income (expense), net	(1,646)	(148)	(1,263)	(426)
Income before provision for income taxes	8,332	5,195	31,681	350
Provision for income taxes	2,164	2,526	5,267	3,747
Net income (loss)	$ 6,168	$ 2,669	$ 26,414	$ (3,397)
Earnings (loss) per share:
Basic (in dollars per share)	$ 0.44	$ 0.19	$ 1.90	$ (0.25)
Diluted (in dollars per share)	$ 0.43	$ 0.19	$ 1.86	$ (0.25)
Shares used in computing earnings (loss) per share:
Basic (in shares)	13,928	13,894	13,935	13,861
Diluted (in shares)	14,205	14,170	14,189	13,861