CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities
Net income (loss)	$ 56,708	$ 344,965	$ (21,826)
Adjustments to reconcile net income (loss) to net cash provided by operating activities
Depreciation and amortization	14,239	16,481	32,729
Provision for severance benefits	8,282	16,743	17,139
Amortization of debt issuance costs and original issue discount	261	2,220	2,299
Loss (gain) on foreign currency, net	32,432	(23,233)	24,692
Provision for inventory reserves	2,244	3,695	10,468
Stock-based compensation	7,704	6,699	6,952
Loss on early extinguishment of borrowings, net	0	766	42
Gain on sale of discontinued operations		(287,117)
Deferred income tax assets	918	(44,441)	35
Other, net	(613)	217	301
Changes in operating assets and liabilities
Accounts receivable, net	7,505	(19,268)	(19,824)
Unbilled accounts receivable, net		14,260	19,274
Inventories	(5,939)	(816)	(14,678)
Other receivables	(21,538)	6,954	(6,200)
Other current assets	12,397	13,561	11,984
Accounts payable	(11,437)	4,907	7,375
Other accounts payable	(7,798)	(12,000)	(8,514)
Accrued expenses	4,637	(26,201)	8,819
Accrued income taxes	(1)	10,825	267
Deferred revenue	(131)	2,174	(4,768)
Other current liabilities	1,445	279	(4,727)
Other non-current liabilities	(1,398)	3,521	(306)
Contributions to severance insurance deposit accounts	(5,688)	(11,921)	(2,262)
Payment of severance benefits	(6,679)	(12,076)	(9,288)
Other, net	193	(3,724)	514
Net cash provided by operating activities	87,743	7,470	50,497
Cash flows from investing activities
Proceeds from settlement of hedge collateral	5,214	13,762	13,583
Payment of hedge collateral	(3,349)	(8,839)	(17,833)
Proceeds from disposal of property, plant and equipment	1,446	65	202
Purchase of property, plant and equipment	(32,212)	(36,100)	(22,955)
Payment for intellectual property registration	(614)	(741)	(1,103)
Collection of guarantee deposits	3,192	1,024	549
Payment of guarantee deposits	(5,001)	(1,236)	(1,349)
Proceeds from sale of discontinued operations		350,553
Other, net	(114)	(6)	9
Net cash provided by (used in) investing activities	(31,438)	318,482	(28,897)
Cash flows from financing activities
Repayment of borrowings		(224,250)	(1,175)
Proceeds from exercise of stock options	4,279	3,918	2,860
Acquisition of treasury stock	(1,653)	(1,125)	(2,702)
Acquisition of stock under accelerated stock repurchase agreement	(20,073)
Payment under accelerated stock repurchase agreement	(17,427)
Repayment of financing related to water treatment facility arrangement	(563)	(546)	(552)
Others	(107)	(278)	(233)
Net cash used in financing activities	(35,544)	(222,281)	(1,802)
Effect of exchange rates on cash and cash equivalents	(21,154)	24,612	(579)
Net increase in cash and cash equivalents	(393)	128,283	19,219
Cash and cash equivalents at beginning of period	279,940	151,657	132,438
Cash and cash equivalents at end of period	279,547	279,940	151,657
Supplemental cash flow information
Cash paid for interest	2,094	22,221	19,071
Cash paid for income taxes	12,672	23,056	2,081
Non-cash investing and financing activities
Property, plant and equipment additions in other accounts payable	747		2,542
Acquisition of treasury stock to satisfy the tax withholding obligations in connection with equity-based compensation	(826)	$ (643)	$ (405)
Exchange of exchangeable senior notes into common stock	$ 83,740