Financial Instruments and Fair Value Measurements - Additional Information (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) Forward_contract	Jun. 30, 2017 USD ($) Forward_contract
Derivatives Fair Value [Line Items]
Number of forward contracts exercised | Forward_contract			31	22
Gains (losses) from forward contracts exercised	$ (1,100,000)	$ 3,600,000	$ (7,900,000)	$ 8,900,000
Hedge ineffectiveness			0	0
Foreign currency translation gains (losses), net	(147,813,000)	3,162,000	(143,043,000)	42,829,000
Forwards [Member]
Derivatives Fair Value [Line Items]
Unrealized gains (losses) on foreign exchange transactions	30,100,000	(18,800,000)	17,200,000	(32,500,000)
Forward Contracts [Member]
Derivatives Fair Value [Line Items]
Foreign currency translation gains (losses), net	$ 64,600,000	$ (7,200,000)	$ 40,300,000	$ (11,300,000)