Derivative Financial Instruments - Classification on the balance sheet for the periods indicated (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Disclosure Of Fair Value Of Derivative Instruments And Their Balance Sheet Classification [Line Items]
Derivative designated as hedging instrument, Interest rate swaps, Other liabilities		$ 321
Foreign currency exchange contracts - foreign currency loan
Disclosure Of Fair Value Of Derivative Instruments And Their Balance Sheet Classification [Line Items]
Total, Asset Derivatives	$ 35
Asset Derivatives
Disclosure Of Fair Value Of Derivative Instruments And Their Balance Sheet Classification [Line Items]
Derivative instruments designated as hedging instruments, Interest rate swaps, Other assets	0	0
Derivatives not designated as hedging instruments, Interest rate swaps, Other assets	161,841	64,463
Derivatives not designated as hedging instruments, Other assets	162,947	65,414
Total, Asset Derivatives	162,947	65,414
Asset Derivatives | Risk participation agreements
Disclosure Of Fair Value Of Derivative Instruments And Their Balance Sheet Classification [Line Items]
Derivatives not designated as hedging instruments, Other assets	888	482
Asset Derivatives | Foreign currency exchange contracts - matched customer book
Disclosure Of Fair Value Of Derivative Instruments And Their Balance Sheet Classification [Line Items]
Derivatives not designated as hedging instruments, Other assets	183	469
Asset Derivatives | Foreign currency exchange contracts - foreign currency loan
Disclosure Of Fair Value Of Derivative Instruments And Their Balance Sheet Classification [Line Items]
Derivatives not designated as hedging instruments, Other assets	35	0
Liability Derivatives
Disclosure Of Fair Value Of Derivative Instruments And Their Balance Sheet Classification [Line Items]
Derivative designated as hedging instrument, Interest rate swaps, Other liabilities	0	321
Derivative not designated as hedging instruments, Interest rate swaps, Other liabilities	48,174	18,057
Derivatives not designated as hedging instruments, Other liabilities	49,774	19,294
Total, Liability Derivatives	49,774	19,615
Liability Derivatives | Risk participation agreements
Disclosure Of Fair Value Of Derivative Instruments And Their Balance Sheet Classification [Line Items]
Derivatives not designated as hedging instruments, Other liabilities	1,382	606
Liability Derivatives | Foreign currency exchange contracts - matched customer book
Disclosure Of Fair Value Of Derivative Instruments And Their Balance Sheet Classification [Line Items]
Derivatives not designated as hedging instruments, Other liabilities	159	428
Liability Derivatives | Foreign currency exchange contracts - foreign currency loan
Disclosure Of Fair Value Of Derivative Instruments And Their Balance Sheet Classification [Line Items]
Derivatives not designated as hedging instruments, Other liabilities	$ 59	$ 203