Cash and Cash Equivalents - Allocation by Currency of Financial Liabilities and Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash and Cash Equivalents [Line Items]
Borrowings	$ 82,921	$ 9,245	$ 13,051
Other financial liabilities	691	608	679
Financial derivatives	1,968	552	743
Financial liabilities	85,580	10,428	14,780
Cash and cash equivalents	270,317	$ 353,537	$ 351,827	$ 323,181
EUR
Cash and Cash Equivalents [Line Items]
Borrowings	3,289
Other financial liabilities	450
Financial derivatives	1,968
Financial liabilities	5,707
Cash and cash equivalents	197,997
GBP
Cash and Cash Equivalents [Line Items]
Borrowings	0
Other financial liabilities	0
Financial derivatives	0
Financial liabilities	0
Cash and cash equivalents	2,887
USD
Cash and Cash Equivalents [Line Items]
Borrowings	75,253
Other financial liabilities	241
Financial derivatives	0
Financial liabilities	75,494
Cash and cash equivalents	29,636
CNY
Cash and Cash Equivalents [Line Items]
Borrowings	4,379
Other financial liabilities	0
Financial derivatives	0
Financial liabilities	4,379
Cash and cash equivalents	3,074
JPY
Cash and Cash Equivalents [Line Items]
Borrowings	0
Other financial liabilities	0
Financial derivatives	0
Financial liabilities	0
Cash and cash equivalents	17,316
KRW
Cash and Cash Equivalents [Line Items]
Borrowings	0
Other financial liabilities	0
Financial derivatives	0
Financial liabilities	0
Cash and cash equivalents	2,531
Other
Cash and Cash Equivalents [Line Items]
Borrowings	0
Other financial liabilities	0
Financial derivatives	0
Financial liabilities	0
Cash and cash equivalents	$ 16,876