Derivative Financial Instruments - Company's derivative financial instruments included in OCI as follows (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Gain in OCI on derivatives	$ 0	$ 3,455	$ 0	$ 47,011
Gain recognized in income on derivatives (ineffective portion and amount excluded from effectiveness test)	0	0	0	0
(Loss) gain recognized in other income for foreign currency exchange contracts:	(1,170)	(1,038)	4,129	(7,249)
Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Gain reclassified from OCI into interest income (effective portion)	8,219	7,134	16,493	10,246
Interest Income | Net Investment Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain recognized in income on derivatives (ineffective portion and amount excluded from effectiveness test)	0	0	0	0
Interest Income | Interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Customer-related positions:	(1,087)	(687)	3,764	(6,967)
Interest Income | Risk participation agreements
Derivative Instruments, Gain (Loss) [Line Items]
Customer-related positions:	(105)	(80)	264	(381)
Other Income
Derivative Instruments, Gain (Loss) [Line Items]
Gain recognized in income on derivatives (ineffective portion and amount excluded from effectiveness test)	0	0	0	0
Other Income | Foreign currency exchange contracts - matched customer book
Derivative Instruments, Gain (Loss) [Line Items]
(Loss) gain recognized in other income for foreign currency exchange contracts:	(14)	96	(8)	69
Other Income | Foreign currency exchange contracts - foreign currency loan
Derivative Instruments, Gain (Loss) [Line Items]
(Loss) gain recognized in other income for foreign currency exchange contracts:	$ 36	$ (367)	$ 109	$ 30