INVESTMENT SECURITIES - ACL for Debt Securities Available-for-Sale (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($)
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]
Beginning Balance	$ 0
Addtions for securities for which no previous expected credit losses were recognized (provision for credit losses)	308
Addtions for securities for which previous expected credit losses were recognized (provision for credit losses)	1,333
Net charge-offs	(331)
Ending Balance	1,310
MBS [Member]
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]
Ending Balance	1,002
MBS [Member] | Private label [Member]
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]
Beginning Balance	0
Addtions for securities for which no previous expected credit losses were recognized (provision for credit losses)	0
Addtions for securities for which previous expected credit losses were recognized (provision for credit losses)	1,333
Net charge-offs	(331)
Ending Balance	1,002
Puerto Rico government obligations [Member]
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]
Beginning Balance	0
Addtions for securities for which no previous expected credit losses were recognized (provision for credit losses)	308
Addtions for securities for which previous expected credit losses were recognized (provision for credit losses)	0
Net charge-offs	0
Ending Balance	$ 308