Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities
Net loss	$ (19,145)	$ (36,908)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	23,956	23,551
Stock-based compensation expense	9,294	10,527
Deferred taxes	0	(42)
Others	333	327
Loss (gain) on sale of assets and other write-offs	(693)	304
Loss on foreign currency hedges	0	2,220
Allowance for doubtful accounts	(17)	(144)
Write-down of inventories	6,750	3,200
Amortization of operating lease right-of-use assets	1,320	0
Foreign currency remeasurement	(2,534)	(4,192)
Issuance of common stock in exchange for research and development services	1,500	0
Change in assets and liabilities, net of effects of asset sale:
Accounts receivable	9,462	519
Inventories	(4,049)	5,482
Prepaid expenses and other assets	1,978	5,957
Accounts payable	(1,096)	(4,958)
Accrued and other liabilities	(8,670)	3,154
Net cash provided by operating activities	18,389	8,997
Cash flows from investing activities
Purchase of property, plant and equipment	(6,247)	(14,377)
Proceeds from sale of property, plant and equipment and other assets	2,138	32
Purchase of marketable securities	(126)	(880)
Proceeds from sale of marketable securities	0	5,000
Proceeds from maturity of marketable securities	0	750
Settlement of foreign currency hedges	0	(1,776)
Net cash used in investing activities	(4,235)	(11,251)
Cash flows from financing activities
Proceeds from exercise of stock options and issuance of stock under ESPP	2,204	3,801
Offering costs	(46)	0
Tax withholding on restricted stock units	(705)	(747)
Proceeds from bank loans, net of debt issuance costs	5,000	29,358
Repayment of bank loans	(12,312)	(57,323)
Proceeds from issuance of notes payable	0	4,795
Repayment of notes payable	(4,806)	(2,568)
Repayment of finance lease liabilities	(60)	0
Proceeds from government grants	0	1,228
Net cash used in financing activities	(10,725)	(21,456)
Effect of exchange rates on cash, cash equivalents and restricted cash	(444)	(560)
Net increase (decrease) in cash, cash equivalents and restricted cash	2,985	(24,270)
Cash, cash equivalents and restricted cash at the beginning of the period	69,238	81,564
Cash, cash equivalents and restricted cash at the end of the period	72,223	57,294
Supplemental disclosure of non-cash investing and financing activities:
Decrease (increase) in unpaid property, plant and equipment	$ (1,278)	$ 8,916