Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets
Inventory cost	$ 8,000	$ 6,923
Accrued expenses and accounts receivable	690	2,112
Foreign tax credits	10,626	19,610
Research and development tax credits	15,828	13,633
Net operating loss carryforwards	5,392	37,379
Accrued pension	5,428	5,494
Share based compensation and others	12,443	16,992
Total deferred tax assets, include valuation allowance	58,407	102,143
Valuation allowances	(22,560)	(32,082)
Total deferred tax assets, non-current	35,847	70,061
Deferred tax liabilities
Plant, equipment and intangible assets	(17,278)	(28,639)
Total deferred tax liabilities, non-current	(17,278)	(28,639)
Net deferred tax assets	$ 18,569	$ 41,422