Derivative Instruments - Derivative Instruments Measured at Fair Value and Classification on Condensed Consolidated Balance Sheets (Detail) - Forward Foreign Exchange Contracts [Member] - Designated As Hedging Instrument [Member] - USD ($)	Jun. 30, 2018	Dec. 31, 2017
Accrued and Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Notional Amount	$ 30,070,000	$ 0
Derivative Fair Value	(1,412,000)	0
Prepaid Expenses and Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Notional Amount	0	66,560,000
Derivative Fair Value	$ 0	$ 551,000