CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets
Cash and cash equivalents	$ 279,547	$ 279,940
Accounts receivable, net	50,954	64,390
Inventories, net	39,370	39,039
Other receivables (Note 19)	25,895	4,338
Prepaid expenses	7,675	7,332
Hedge collateral (Note 10)	3,060	5,250
Other current assets	2,619	9,321
Total current assets	409,120	409,610
Property, plant and equipment, net	107,882	96,383
Operating lease right-of-use assets	4,275	4,632
Intangible assets, net	2,377	2,727
Long-term prepaid expenses	8,243	4,058
Deferred income taxes (Note 17)	41,095	44,541
Other non-current assets	10,662	9,739
Total assets	583,654	571,690
Current liabilities
Accounts payable	37,593	52,164
Other accounts payable	6,289	2,531
Accrued expenses (Note 9)	20,071	16,241
Accrued income taxes	11,823	12,398
Operating lease liabilities	2,323	2,210
Current portion of long-term borrowings, net		83,479
Other current liabilities	7,382	4,595
Total current liabilities	85,481	173,618
Accrued severance benefits, net	33,064	40,462
Non-current operating lease liabilities	1,952	2,422
Other non-current liabilities	10,395	9,588
Total liabilities	130,892	226,090
Commitments and contingencies (Note 20)
Stockholders' equity
Common stock, $0.01 par value, 150,000,000 shares authorized, 55,905,320 shares issued and 45,659,304 outstanding at December 31, 2021 and 44,943,854 shares issued and 35,783,347 outstanding at December 31, 2020	559	450
Additional paid-in capital	241,197	163,010
Retained earnings	343,542	286,834
Treasury stock, 10,246,016 shares at December 31, 2021 and 9,160,507 shares at December 31, 2020, respectively	(130,306)	(108,397)
Accumulated other comprehensive income (loss)	(2,230)	3,703
Total stockholders' equity	452,762	345,600
Total liabilities and stockholders' equity	$ 583,654	$ 571,690