Income Taxes - Components of Net Deferred Tax Assets (Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Foreign tax credit carryforward	$ 6,549	$ 4,817
Inventory	13,536	17,777
Net operating losses	1,250	18,991
Allowance for doubtful accounts	490	358
Reserve for accrued liabilities	4,029	2,732
Stock options	1,670	2,782
Unrealized gain/loss	1,554	1,862
Disallowed interest carryforward	1,912
Other	1,939	867
Total deferred tax assets	32,929	50,186
Valuation allowance	(17,049)	(34,464)
Deferred tax liabilities:
Property, plant and equipment	(6,048)	(5,757)
Goodwill & Intangibles	(1,903)	(2,092)
Deferred revenue	(3,415)	(1,830)
Reserve for unremitted earnings	(3,608)
Other	(1,917)	(1,257)
Total deferred tax liability	(16,891)	(10,936)
Net deferred tax liability	$ (1,011)
Net deferred tax asset		$ 4,786