Financial Instruments - Derivative Instruments Notional Amount Outstanding (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Forward Contracts [Member]
Schedule Of Information By Major Category Of Credit Derivatives Contracts [Line Items]
Derivative instruments outstanding	$ 411,436	$ 585,581
Currency Swap
Schedule Of Information By Major Category Of Credit Derivatives Contracts [Line Items]
Derivative instruments outstanding	$ 600,000	$ 600,000

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

Name:	invest_DerivativeNotionalAmount
Namespace Prefix:	invest_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant