LOANS HELD FOR INVESTMENT - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 11,206,874		$ 11,206,874			$ 11,060,658
Financing Receivable, Troubled Debt Restructuring	394,500		394,500
Interest Receivable	62,501		62,501			61,507
Financing Receivable Allowance For Credit Losses	252,152	$ 324,958	252,152	$ 324,958	$ 245,447	269,030	$ 358,936	$ 385,887
Financing Receivable, Allowance for Credit Loss, Writeoff	12,592	17,866	25,307	34,100
Loans and finance leases	12,665	(26,302)	(4,324)	(40,745)
Interest Income Recognized on Nonaccrual Loans	300	800	700	1,300
United States [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,989,147		1,989,147			1,946,740
Performing loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Troubled Debt Restructuring	345,400		345,400			$ 363,400
Nonaccrual loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable Accrued Interest Writeoff	$ 300	300	$ 700	1,300
Collateral Pledged [Member] | Weighted Average [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
LTV Coverage %	79.00%		79.00%			78.00%
Loans and Finance Receivables [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest Receivable	$ 47,100		$ 47,100			$ 48,100
Loans and Finance Receivables [Member] | Puerto Rico [Member] | Product Concentration Risk [Member] | Loan Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Credit risk concentration			79.00%
Loans and Finance Receivables [Member] | United States [Member] | Product Concentration Risk [Member] | Loan Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Credit risk concentration			18.00%
Loans and Finance Receivables [Member] | USVI and BVI [Member] | Product Concentration Risk [Member] | Loan Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Credit risk concentration			3.00%
GNMA [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in loans			$ 79,700	105,900
Residential Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,851,685		2,851,685			2,978,895
Residential mortgage loans in process of foreclosure	84,800		$ 84,800
Loans Foreclosure Delinquency Threshold			120 days
Financing Receivable, Real Estate Acquired Through Foreclosure [Policy Text Block]			The Corporation commences the foreclosure process on residential real estate loans when a borrower becomes 120 days delinquent, in accordance with the requirements of the Consumer Financial Protection Bureau (“CFPB”). Foreclosure procedures and timelines vary depending on whether the property is located in a judicial or non-judicial state. Occasionally, foreclosures may be delayed due to, among other reasons, mandatory mediations, bankruptcy, court delays and title issues.
Financing Receivable Allowance For Credit Losses	65,231	112,882	$ 65,231	112,882	68,820	74,837	114,044	120,311
Financing Receivable, Allowance for Credit Loss, Writeoff	2,079	2,927	4,607	5,752
Loans and finance leases	(2,797)	825	(7,668)	(3,350)
Residential Portfolio Segment [Member] | TDR [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans in trial			1,900
Residential Portfolio Segment [Member] | Government [Member] | PRHFA [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	88,500		88,500			92,800
Residential Portfolio Segment [Member] | United States [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	407,153		407,153			429,322
Residential Portfolio Segment [Member] | Performing loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,807,097		2,807,097			2,923,768
Residential Portfolio Segment [Member] | Performing loans [Member] | United States [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	401,181		401,181			422,170
Residential Portfolio Segment [Member] | Nonaccrual loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	44,588		44,588			55,127
Residential Portfolio Segment [Member] | Nonaccrual loans [Member] | United States [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	5,972		5,972			7,152
Residential Portfolio Segment [Member] | PCD loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Residential mortgage loans in process of foreclosure	12,100		12,100
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,730,525		2,730,525			2,853,503
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | TDR [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Troubled Debt Restructuring	245,400		245,400
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | United States [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	406,421		406,421			428,582
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | Performing loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,685,937		2,685,937			2,798,376
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | Performing loans [Member] | United States [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	400,449		400,449			421,430
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | Nonaccrual loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	44,588		44,588			55,127
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | Nonaccrual loans [Member] | United States [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	5,972		5,972			7,152
Residential Portfolio Segment [Member] | FHA/VA government-guaranteed loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	121,160		121,160			125,392
Residential mortgage loans in process of foreclosure	35,100		35,100
Financing Receivable, Troubled Debt Restructuring	55,100		55,100			57,600
Residential Portfolio Segment [Member] | FHA/VA government-guaranteed loans [Member] | United States [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	732		732			740
Residential Portfolio Segment [Member] | FHA/VA government-guaranteed loans [Member] | Performing loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	121,160		121,160			125,392
Residential Portfolio Segment [Member] | FHA/VA government-guaranteed loans [Member] | Performing loans [Member] | United States [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	732		732			740
Residential Portfolio Segment [Member] | FHA/VA government-guaranteed loans [Member] | Nonaccrual loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	0		0			0
Residential Portfolio Segment [Member] | FHA/VA government-guaranteed loans [Member] | Nonaccrual loans [Member] | United States [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	0		0			0
Residential Portfolio Segment [Member] | FNMA and FHLMC Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Purchase			200	300
Residential Portfolio Segment [Member] | FNMA and FHLMC Loans | Performing loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Sale			78,400	191,400
Residential Portfolio Segment [Member] | GNMA [Member] | Repurchase Option Program [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	10,800		10,800			7,200
Financing Receivable, Purchase			6,200	300
Commercial Portfolio Segment [Member] | Criticized [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Sale				24,000
Commercial Portfolio Segment [Member] | Puerto Rico [Member] | Government [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	171,400		171,400			178,400
Commercial Portfolio Segment [Member] | Puerto Rico [Member] | Government [Member] | Municipalities Borrower [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	28,700		28,700
Commercial Portfolio Segment [Member] | Puerto Rico [Member] | Government [Member] | PREPA [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	11,700		11,700
Commercial Portfolio Segment [Member] | Puerto Rico [Member] | Government [Member] | Property Tax Revenue [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	99,700		99,700
Commercial Portfolio Segment [Member] | Puerto Rico [Member] | Government [Member] | Municipal Special Obligation Bond [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	31,300		31,300
Commercial Portfolio Segment [Member] | USVI [Member] | Government [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	39,500		39,500			39,200
Commercial Portfolio Segment [Member] | Construction loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	115,310		115,310			138,999
Financing Receivable Allowance For Credit Losses	2,020	4,757	2,020	4,757	1,842	4,048	4,915	5,380
Financing Receivable, Allowance for Credit Loss, Writeoff	16	0	60	45
Loans and finance leases	151	(196)	(2,063)	(652)
Commercial Portfolio Segment [Member] | Construction loans [Member] | TDR [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Troubled Debt Restructuring	1,600		1,600
Commercial Portfolio Segment [Member] | Construction loans [Member] | United States [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	89,833		89,833			95,866
Commercial Portfolio Segment [Member] | Mortgage Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,270,113		2,270,113			2,167,469
Financing Receivable Allowance For Credit Losses	32,619	72,452	32,619	72,452	30,138	52,771	99,782	109,342
Financing Receivable, Allowance for Credit Loss, Writeoff	2	81	39	875
Loans and finance leases	1,265	(27,299)	(21,375)	(36,119)
Commercial Portfolio Segment [Member] | Mortgage Receivable [Member] | TDR [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Troubled Debt Restructuring	65,400		65,400
Commercial Portfolio Segment [Member] | Mortgage Receivable [Member] | United States [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	485,234		485,234			465,238
Commercial Portfolio Segment [Member] | Commercial And Industrial Sector [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,862,917		2,862,917			2,887,251
Financing Receivable Allowance For Credit Losses	36,203	37,470	36,203	37,470	36,784	34,284	32,087	37,944
Financing Receivable, Allowance for Credit Loss, Writeoff	68	60	358	869
Loans and finance leases	(1,102)	(426)	653	(5,738)
Commercial Portfolio Segment [Member] | Commercial And Industrial Sector [Member] | TDR [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Troubled Debt Restructuring	68,700		68,700
Commercial Portfolio Segment [Member] | Commercial And Industrial Sector [Member] | United States [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	993,707		993,707			940,654
Financing Receivable, Purchase			76,400	50,000
Consumer Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,106,849		3,106,849			2,888,044
Financing Receivable Allowance For Credit Losses	116,079	97,397	116,079	97,397	$ 107,863	103,090	$ 108,108	$ 112,910
Financing Receivable, Allowance for Credit Loss, Writeoff	10,427	14,798	20,243	26,559
Loans and finance leases	15,148	$ 794	26,129	$ 5,114
Consumer Portfolio Segment [Member] | TDR [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Troubled Debt Restructuring	13,400		13,400
Outstanding unfunded commitments on TDR loans	10		10
Consumer Portfolio Segment [Member] | United States [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	13,220		13,220			15,660
Consumer Portfolio Segment [Member] | Performing loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	3,096,534		3,096,534			2,877,590
Consumer Portfolio Segment [Member] | Performing loans [Member] | United States [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	13,016		13,016			15,527
Consumer Portfolio Segment [Member] | Nonaccrual loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	10,315		10,315			10,454
Consumer Portfolio Segment [Member] | Nonaccrual loans [Member] | United States [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 204		$ 204			$ 133