Derivative Instruments and Hedging Activities - Open Foreign Currency Contracts (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Net Unrealized Loss	$ (426)	$ 298
Cash Flow Hedging | Foreign currency contracts
Derivative [Line Items]
Notional Amounts (in U.S. dollars)	128,541
Net Unrealized Loss	(426)
Australian Dollar | Cash Flow Hedging | Foreign currency contracts
Derivative [Line Items]
Notional Amounts (in U.S. dollars)	24,250
Net Unrealized Loss	(134)
Canadian Dollar | Cash Flow Hedging | Foreign currency contracts
Derivative [Line Items]
Notional Amounts (in U.S. dollars)	94,292
Net Unrealized Loss	(159)
Mexican Peso | Cash Flow Hedging | Foreign currency contracts
Derivative [Line Items]
Notional Amounts (in U.S. dollars)	9,999
Net Unrealized Loss	$ (133)