Change in Fair Value of Forward Contracts (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) from the change in the fair value of forward contracts included in other income (expense), net		$ (1,237)	$ 286	$ (4,955)
Foreign currency transaction (loss) gain from the remeasurement of foreign currency assets and liabilities	$ (552)	1,082	(793)	2,764
Net gain (loss)	$ (552)	$ (155)	$ (507)	$ (2,191)