Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Deferred tax assets:
Net operating losses	$ 14,054		$ 23,490
Foreign tax credits	7,304		9,262
Accruals not currently deductible	3,209		7,730
Unrealized foreign exchange losses, net	3,575		2,595
Stock-based compensation	3,266		3,793
Capitalized inventory costs	1,972		4,581
Alternative minimum tax carryforwards	2,198		1,626
Other	6,631		8,825
Total deferred tax assets	42,209		61,902
Valuation allowance	(23,842)		(30,154)
Total deferred tax assets, net of allowances	18,367		31,748
Deferred tax liabilities:
Accelerated depreciation and amortization	(29,656)		(34,265)
Tax on unremitted earnings	(16,174)		(16,821)
Original issue discount on 2021 Convertible Notes	(3,347)		(4,299)
Other	(2,160)		(3,190)
Total deferred tax liabilities	(51,337)		(58,575)
Total net deferred tax liabilities	(32,970)		(26,827)
Noncurrent deferred tax assets	4,516		4,753
Noncurrent deferred tax liabilities	(37,486)	$ (35,386)	(31,580)
Net deferred tax liabilities	$ (32,970)		$ (26,827)