Derivative Instruments and Hedging Activities Carrying Values of Derivative Instruments (Detail) - USD ($) $ in Thousands		Sep. 30, 2018	Dec. 31, 2017
Derivative [Line Items]
Derivative Net Carrying Value		$ 3,789	$ (426)
Designated as Hedging Instrument
Derivative [Line Items]
Derivative Net Carrying Value		3,789	(426)
Designated as Hedging Instrument | Foreign Exchange Contract
Derivative [Line Items]
Derivative Net Carrying Value	[1]	3,010	(426)
Designated as Hedging Instrument | Interest rate contract
Derivative [Line Items]
Derivative Net Carrying Value	[1]	779
Prepaid Expenses And Other Current Assets
Derivative [Line Items]
Fair Value— Assets		3,789	621
Prepaid Expenses And Other Current Assets | Designated as Hedging Instrument
Derivative [Line Items]
Fair Value— Assets		3,789	621
Prepaid Expenses And Other Current Assets | Designated as Hedging Instrument | Foreign Exchange Contract
Derivative [Line Items]
Fair Value— Assets	[1]	3,010	621
Prepaid Expenses And Other Current Assets | Designated as Hedging Instrument | Interest rate contract
Derivative [Line Items]
Fair Value— Assets	[1]	779
Other Current Liabilities
Derivative [Line Items]
Fair Value— (Liabilities)		0	(1,047)
Other Current Liabilities | Designated as Hedging Instrument
Derivative [Line Items]
Fair Value— (Liabilities)		0	(1,047)
Other Current Liabilities | Designated as Hedging Instrument | Foreign Exchange Contract
Derivative [Line Items]
Fair Value— (Liabilities)	[1]	0	$ (1,047)
Other Current Liabilities | Designated as Hedging Instrument | Interest rate contract
Derivative [Line Items]
Fair Value— (Liabilities)	[1]	$ 0

[1] Assets are included in prepaid expenses and other and liabilities are included in other accrued expenses on the accompanying consolidated balance sheets.