CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities
Net income (loss)	$ (10,692)	$ 6,307
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation and amortization	6,381	6,674
Stock-based compensation expense	3,277	2,518
Deferred taxes	344	1,214
Others	108	86
Gain on sale of assets and other write-offs	(17)	(25)
Write-down of inventories	2,267	3,011
Amortization of operating lease right-of-use assets	508	462
Foreign currency remeasurement	(968)	(1,118)
Change in operating assets and liabilities:
Accounts receivable	5,255	7,209
Inventories	(2,260)	(2,699)
Prepaid expenses and other assets	3,441	(469)
Accounts payable	(5,526)	523
Accrued and other liabilities	(11,062)	1,233
Net cash provided by (used in) operating activities	(8,944)	24,926
Cash flows from investing activities
Purchase of property, plant and equipment	(1,908)	(2,578)
Proceeds from sale of property, plant and equipment and other assets	358	109
Purchase of marketable securities	(13,503)	(24)
Proceeds from sale of marketable securities	13,501	0
Net cash used in investing activities	(1,552)	(2,493)
Cash flows from financing activities
Proceeds from exercise of stock options and issuance of stock under ESPP	1,548	231
Tax withholding on restricted stock units	(1,835)	(219)
Repayment of bank loans	(794)	(1,772)
Repayment of finance lease liabilities	(24)	(21)
Net cash used in financing activities	(1,105)	(1,781)
Effect of exchange rates on cash, cash equivalents and restricted cash	(449)	(254)
Net increase (decrease) in cash, cash equivalents and restricted cash	(12,050)	20,398
Cash, cash equivalents and restricted cash at the beginning of the period	95,606	81,439
Cash, cash equivalents and restricted cash at the end of the period	83,556	101,837
Supplemental disclosure of non-cash investing and financing activities:
Unpaid property, plant and equipment in accounts payable	$ 862	$ 1,130