CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Cash flows from operating activities
Net income (loss)	$ (29,984)	$ 7,129
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation and amortization	18,220	24,096
Stock-based compensation expense	7,811	9,078
Deferred taxes	960	(4)
Others	248	269
Gain on sale of assets and other write-offs	33	(47)
Allowance for doubtful accounts	(1)	(16)
Write-down of inventories	9,215	7,236
Amortization of operating lease right-of-use assets	1,549	1,415
Foreign currency remeasurement	(110)	2,309
Change in operating assets and liabilities:
Accounts receivable	(12,671)	8,790
Inventories	(11,438)	(6,592)
Prepaid expenses and other assets	(582)	(1,315)
Accounts payable	15,587	(4,052)
Accrued and other liabilities	(20,454)	1,218
Net cash provided by (used in) operating activities	(21,617)	49,514
Cash flows from investing activities
Purchase of property, plant and equipment	(9,150)	(9,243)
Proceeds from sale of property, plant and equipment and other assets	1,023	507
Purchase of marketable securities	(27,506)	(23,529)
Proceeds from sale of marketable securities	27,501	3,500
Net cash used in investing activities	(8,132)	(28,765)
Cash flows from financing activities
Proceeds from exercise of stock options and issuance of stock under ESPP	4,946	2,719
Tax withholding on restricted stock units	(4,952)	(1,722)
Proceeds from bank loans, net of debt issuance costs	14,979	0
Repayment of bank loans	(3,626)	(8,349)
Repayment of finance lease liabilities	(70)	(64)
Net cash provided by (used in) financing activities	11,277	(7,416)
Effect of exchange rates on cash, cash equivalents and restricted cash	(61)	502
Net increase (decrease) in cash, cash equivalents and restricted cash	(18,533)	13,835
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	77,073	95,274
Supplemental disclosure of non-cash investing and financing activities:
Unpaid property, plant and equipment in accounts payable	1,192	1,811
Right-of-use asset in exchange for a lease liability	$ 1,639	$ 0