Fair Value Measurement (Details) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Assets:
Short-term investments	$ 122,402	$ 94,202
Foreign currency forward exchange contracts accounted for using hedge accounting	1,230
Total Assets	123,632
Liabilities:
Foreign currency forward exchange contracts accounted for using hedge accounting		181
Foreign currency forward exchange contracts not accounted for using hedge accounting	310	418
Interest rate swap	628	908
Total Liabilities	938	1,507
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets:
Short-term investments
Foreign currency forward exchange contracts accounted for using hedge accounting
Total Assets
Liabilities:
Foreign currency forward exchange contracts accounted for using hedge accounting
Foreign currency forward exchange contracts not accounted for using hedge accounting
Interest rate swap
Total Liabilities
Significant Other Observable Inputs (Level 2) [Member]
Assets:
Short-term investments	122,402	94,202
Foreign currency forward exchange contracts accounted for using hedge accounting	1,230
Total Assets	123,632
Liabilities:
Foreign currency forward exchange contracts accounted for using hedge accounting		181
Foreign currency forward exchange contracts not accounted for using hedge accounting	310	418
Interest rate swap	628	908
Total Liabilities	938	1,507
Significant Unobservable Inputs (Level 3) [Member]
Assets:
Short-term investments
Foreign currency forward exchange contracts accounted for using hedge accounting
Total Assets
Liabilities:
Foreign currency forward exchange contracts accounted for using hedge accounting
Foreign currency forward exchange contracts not accounted for using hedge accounting
Interest rate swap
Total Liabilities