Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Foreign Exchange Contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets (Liabilities)	$ (85)	$ (3,227)
Stock-based Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets (Liabilities)	(12,077)	(16,713)
Quoted Prices in Active Markets for Identical Assets Level (1) | Stock-based Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets (Liabilities)	(12,077)	(16,713)
Significant Other Observable Inputs Level (2) | Foreign Exchange Contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets (Liabilities)	$ (85)	$ (3,227)