Fair Value Measurements (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Recurring basis
Financial instruments carried at fair value (asset position):
Total financial assets	$ 928,109	$ 546,765
Financial instruments carried at fair value (liability position):
Total financial liabilities	(14,874)	(144)
Recurring basis \| Level 1
Financial instruments carried at fair value (asset position):
Total financial assets	538,625	360,628
Financial instruments carried at fair value (liability position):
Total financial liabilities	0	0
Recurring basis \| Level 2
Financial instruments carried at fair value (asset position):
Total financial assets	389,484	186,137
Financial instruments carried at fair value (liability position):
Total financial liabilities	(14,874)	(144)
Recurring basis \| Level 3
Financial instruments carried at fair value (asset position):
Total financial assets	0	0
Financial instruments carried at fair value (liability position):
Total financial liabilities	0	0
Prepaid and other current assets \| Foreign currency forward contracts \| Recurring basis
Financial instruments carried at fair value (asset position):
Foreign currency forward contracts	42	14,407
Prepaid and other current assets \| Foreign currency forward contracts \| Recurring basis \| Level 1
Financial instruments carried at fair value (asset position):
Foreign currency forward contracts	0	0
Prepaid and other current assets \| Foreign currency forward contracts \| Recurring basis \| Level 2
Financial instruments carried at fair value (asset position):
Foreign currency forward contracts	42	14,407
Prepaid and other current assets \| Foreign currency forward contracts \| Recurring basis \| Level 3
Financial instruments carried at fair value (asset position):
Foreign currency forward contracts	0	0
Other assets \| Foreign currency forward contracts \| Recurring basis
Financial instruments carried at fair value (asset position):
Foreign currency forward contracts	8	1,186
Other assets \| Foreign currency forward contracts \| Recurring basis \| Level 1
Financial instruments carried at fair value (asset position):
Foreign currency forward contracts	0	0
Other assets \| Foreign currency forward contracts \| Recurring basis \| Level 2
Financial instruments carried at fair value (asset position):
Foreign currency forward contracts	8	1,186
Other assets \| Foreign currency forward contracts \| Recurring basis \| Level 3
Financial instruments carried at fair value (asset position):
Foreign currency forward contracts	0	0
Other liabilities, current portion \| Foreign currency forward contracts \| Recurring basis
Financial instruments carried at fair value (liability position):
Derivative liability current	(13,897)	(144)
Other liabilities, current portion \| Foreign currency forward contracts \| Recurring basis \| Level 1
Financial instruments carried at fair value (liability position):
Derivative liability current	0	0
Other liabilities, current portion \| Foreign currency forward contracts \| Recurring basis \| Level 2
Financial instruments carried at fair value (liability position):
Derivative liability current	(13,897)	(144)
Other liabilities, current portion \| Foreign currency forward contracts \| Recurring basis \| Level 3
Financial instruments carried at fair value (liability position):
Derivative liability current	0	0
Other liabilities, excluding current portion \| Foreign currency forward contracts \| Recurring basis
Financial instruments carried at fair value (liability position):
Derivative liability, noncurrent	(977)
Other liabilities, excluding current portion \| Foreign currency forward contracts \| Recurring basis \| Level 1
Financial instruments carried at fair value (liability position):
Derivative liability, noncurrent	0
Other liabilities, excluding current portion \| Foreign currency forward contracts \| Recurring basis \| Level 2
Financial instruments carried at fair value (liability position):
Derivative liability, noncurrent	(977)
Other liabilities, excluding current portion \| Foreign currency forward contracts \| Recurring basis \| Level 3
Financial instruments carried at fair value (liability position):
Derivative liability, noncurrent	0
Money market funds \| Recurring basis
Financial instruments carried at fair value (asset position):
Cash equivalents	466,702	280,560
Money market funds \| Recurring basis \| Level 1
Financial instruments carried at fair value (asset position):
Cash equivalents	466,702	280,560
Money market funds \| Recurring basis \| Level 2
Financial instruments carried at fair value (asset position):
Cash equivalents	0	0
Money market funds \| Recurring basis \| Level 3
Financial instruments carried at fair value (asset position):
Cash equivalents	0	0
Government-sponsored enterprise securities \| Recurring basis
Financial instruments carried at fair value (asset position):
Cash equivalents	14,979
Marketable securities		15,508
Government-sponsored enterprise securities \| Recurring basis \| Level 1
Financial instruments carried at fair value (asset position):
Cash equivalents	14,979
Marketable securities		15,508
Government-sponsored enterprise securities \| Recurring basis \| Level 2
Financial instruments carried at fair value (asset position):
Cash equivalents	0
Marketable securities		0
Government-sponsored enterprise securities \| Recurring basis \| Level 3
Financial instruments carried at fair value (asset position):
Cash equivalents	0
Marketable securities		0
Corporate debt securities \| Recurring basis
Financial instruments carried at fair value (asset position):
Cash equivalents	4,488
Marketable securities	295,171	111,140
Corporate debt securities \| Recurring basis \| Level 1
Financial instruments carried at fair value (asset position):
Cash equivalents	0
Marketable securities	0	0
Corporate debt securities \| Recurring basis \| Level 2
Financial instruments carried at fair value (asset position):
Cash equivalents	4,488
Marketable securities	295,171	111,140
Corporate debt securities \| Recurring basis \| Level 3
Financial instruments carried at fair value (asset position):
Cash equivalents	0
Marketable securities	0	0
Commercial paper \| Recurring basis
Financial instruments carried at fair value (asset position):
Cash equivalents	14,608
Marketable securities	75,167	59,404
Commercial paper \| Recurring basis \| Level 1
Financial instruments carried at fair value (asset position):
Cash equivalents	0
Marketable securities	0	0
Commercial paper \| Recurring basis \| Level 2
Financial instruments carried at fair value (asset position):
Cash equivalents	14,608
Marketable securities	75,167	59,404
Commercial paper \| Recurring basis \| Level 3
Financial instruments carried at fair value (asset position):
Cash equivalents	0
Marketable securities	0	0
Corporate equity securities \| Recurring basis
Financial instruments carried at fair value (asset position):
Marketable securities	56,944	64,560
Corporate equity securities \| Recurring basis \| Level 1
Financial instruments carried at fair value (asset position):
Marketable securities	56,944	64,560
Corporate equity securities \| Recurring basis \| Level 2
Financial instruments carried at fair value (asset position):
Marketable securities	0	0
Corporate equity securities \| Recurring basis \| Level 3
Financial instruments carried at fair value (asset position):
Marketable securities	0	$ 0
Variable Interest Entity, Primary Beneficiary \| Level 1
Financial instruments carried at fair value (liability position):
Cash and cash equivalents	$ 1,500

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
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