Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Net operating losses	$ 14,205	$ 14,054
Foreign tax credits	5,651	7,304
Accruals not currently deductible	4,928	3,209
Unrealized foreign exchange losses, net	3,837	3,575
Stock-based compensation	3,380	3,266
Capitalized inventory costs	1,611	1,972
Alternative minimum tax carryforwards	369	2,198
Other	6,709	6,631
Total deferred tax assets	40,690	42,209
Valuation allowance	(23,962)	(23,842)
Total deferred tax assets, net of allowances	16,728	18,367
Deferred tax liabilities:
Accelerated depreciation and amortization	(28,703)	(29,656)
Tax on unremitted earnings	(13,645)	(16,174)
Original issue discount on 2021 Convertible Notes	(2,311)	(3,347)
Other	(2,716)	(2,160)
Total deferred tax liabilities	(47,375)	(51,337)
Net deferred tax liabilities	(30,647)	(32,970)
Noncurrent deferred tax assets	3,600	4,516
Noncurrent deferred tax liabilities	(34,247)	(37,486)
Net deferred tax liabilities	$ (30,647)	$ (32,970)