Financial Instruments - Derivative Instruments Notional Amount Outstanding (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Forward Currency Contracts [Member]
Schedule Of Information By Major Category Of Credit Derivatives Contracts [Line Items]
Derivative instruments outstanding	$ 585,581	$ 896,947
Currency Swap [Member]
Schedule Of Information By Major Category Of Credit Derivatives Contracts [Line Items]
Derivative instruments outstanding	1,087	0
Interest Rate Swap [Member]
Schedule Of Information By Major Category Of Credit Derivatives Contracts [Line Items]
Derivative instruments outstanding	$ 0	$ 150,000