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Fair Value Measurement (Details) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Assets:
Short-term investments	$ 81,813	$ 69,899
Foreign currency forward exchange contracts accounted for using hedge accounting		26
Foreign currency forward exchange contracts not accounted for using hedge accounting		119
Total Assets		70,044
Liabilities:
Interest rate swap	463	529
Foreign currency forward exchange contracts accounted for using hedge accounting	140
Foreign currency forward exchange contracts not accounted for using hedge accounting	7
Total Liabilities	610
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
Foreign currency forward exchange contracts not accounted for using hedge accounting
Total Assets
Liabilities:
Interest rate swap
Foreign currency forward exchange contracts accounted for using hedge accounting
Foreign currency forward exchange contracts not accounted for using hedge accounting
Total Liabilities
Significant Other Observable Inputs (Level 2) [Member]
Assets:
Short-term investments	81,813	69,899
Foreign currency forward exchange contracts accounted for using hedge accounting		26
Foreign currency forward exchange contracts not accounted for using hedge accounting		119
Total Assets		70,044
Liabilities:
Interest rate swap	463	529
Foreign currency forward exchange contracts accounted for using hedge accounting	140
Foreign currency forward exchange contracts not accounted for using hedge accounting	7
Total Liabilities	610
Significant Unobservable Inputs (Level 3) [Member]
Assets:
Short-term investments
Foreign currency forward exchange contracts accounted for using hedge accounting
Foreign currency forward exchange contracts not accounted for using hedge accounting
Total Assets
Liabilities:
Interest rate swap
Foreign currency forward exchange contracts accounted for using hedge accounting
Foreign currency forward exchange contracts not accounted for using hedge accounting
Total Liabilities