Derivatives - Net Gains (Losses) with Respect to Derivative Instruments Not Designated as Hedging Instruments (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives instruments	$ 609	$ (11,266)
Forward Foreign Currency Exchange Rate Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as hedging instruments	(2,483)	1,472
LFI and Other Similar Deferred Compensation Arrangements [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as hedging instruments	1,436	(7,353)
Total Return Swaps and Other [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives designated as hedging instruments	$ 1,656	$ (5,385)