Derivative Financial Instruments - Summary of (Gain) Loss Reclassified From Accumulated Other Comprehensive Loss Earnings For Derivatives (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Derivative Instruments Gain Loss [Line Items]
(Gain) loss on derivative hedging instruments	$ (4,151)	$ 16,950
Cross Currency Swap Agreements [Member] | Designated as Hedging Instrument [Member] | Other Non-operating (Income) Expense, Net [Member]
Derivative Instruments Gain Loss [Line Items]
(Gain) loss on derivative hedging instruments	(2,969)	13,242
Cross Currency Swap Agreements [Member] | Not Designated as Hedging Instrument [Member] | Other Non-operating (Income) Expense, Net [Member]
Derivative Instruments Gain Loss [Line Items]
(Gain) loss on derivative hedging instruments	$ (1,182)	$ 3,708