Derivatives and Hedging - Additional Information (Detail) - USD ($)	Jun. 30, 2018	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount of derivative assets and liabilities	$ 250,700,000	$ 239,400,000
Designated as Cash Flow Hedges
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount of derivative assets and liabilities	0	3,900,000
Foreign Exchange Contracts | Designated as Cash Flow Hedges
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount of derivative assets and liabilities	$ 0	$ 3,900,000