CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows provided by operating activities:
Net (loss) income	$ (1,412)	$ 34,041	$ 30,473
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation	9,632	8,316	6,576
Amortization of purchased intangible assets	1,449	1,544	2,944
Amortization and write-off of deferred debt issuance costs	207	178	314
Stock-based compensation	5,675	5,204	3,580
Deferred income tax benefit	(2,313)	4,289	(3,653)
Loss on disposal of property, plant and equipment	247	530	78
Restructuring expenses, net and asset impairments	3,387	19,503	1,114
Transition tax liability	0	0	(679)
Change in:
Accounts receivable, net	30,227	(1,221)	(11,409)
Inventories	2,992	(2,671)	(16,610)
Prepaid expenses and other	675	(5,724)	491
Accounts payable	(14,772)	10,145	2,197
Contract liabilities	1,985	1,603	(4,721)
Accrued anti-dumping duties and penalties	0	(8,000)	4,391
Accrued expenses and other liabilities	(7,617)	(3,143)	12,552
Net cash provided by operating activities	30,362	64,594	27,638
Cash flows used in investing activities:
Investment in marketable securities	(25,740)	0	0
Acquisition of property, plant and equipment	(13,853)	(27,210)	(45,095)
Proceeds on sale of property, plant and equipment	36	1,263	0
Net cash used in investing activities	(39,557)	(25,947)	(45,095)
Cash flows provided by (used in) financing activities:
Payments on revolving loans, net	0	(17,129)	(1,628)
(Payments) borrowings on capital expenditure facility	(3,125)	(10,125)
(Payments) borrowings on capital expenditure facility			25,000
Payment of dividends	(3,749)	(2,762)	(1,189)
Payment of deferred debt issuance costs	(90)	0	(314)
Net proceeds from issuance of common stock through at-the-market offering program	25,740	0	0
Net proceeds from issuance of common stock to employees and directors	431	557	442
Treasury stock purchases	(1,890)	(1,103)	(453)
Net cash provided by (used in) financing activities	17,317	(30,562)	21,858
Effects of exchange rates on cash	(288)	(1,107)	(9)
Net increase in cash and cash equivalents	7,834	6,978	4,392
Cash and cash equivalents, beginning of the period	20,353	13,375	8,983
Cash and cash equivalents, end of the period	28,187	20,353	13,375
Supplemental disclosure of cash flow information:
Non-cash lease liabilities arising from obtaining right-of-use assets	0	8,821	0
Cash paid during the period for -
Interest	402	1,445	1,383
Income taxes, net	$ 497	$ 20,995	$ 1,284