Assets and Liabilities Measured at Fair Value (Detail) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Fair Value Assets
Total marketable securities	$ 63,812	$ 63,167
Foreign currency forward contracts
Fair Value Assets
Foreign currency forward contracts		628
Fair Value Liabilities
Foreign currency forward contracts		883
Money Market Funds
Fair Value Assets
Money market funds	655	458
Municipal bonds
Fair Value Assets
Total marketable securities	32,759	36,607
Corporate bonds
Fair Value Assets
Total marketable securities	31,053	26,560
Level 1 | Money Market Funds
Fair Value Assets
Money market funds	655	458
Level 2
Fair Value Assets
Total marketable securities	63,812	63,167
Level 2 | Foreign currency forward contracts
Fair Value Assets
Foreign currency forward contracts		628
Fair Value Liabilities
Foreign currency forward contracts		883
Level 2 | Municipal bonds
Fair Value Assets
Total marketable securities	32,759	36,607
Level 2 | Corporate bonds
Fair Value Assets
Total marketable securities	$ 31,053	$ 26,560