LOANS HELD FOR INVESTMENT - Breakdown Between Accrual and Nonaccrual Status of TDRs (Detail) - Entity Loan Modification Program [Member] - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	$ 401,603	$ 398,257
Financing Receivable Modifications Recorded Investment Nonaccrual Status	95,692	89,740
Financing Receivable, Troubled Debt Restructuring	497,295	487,997	$ 589,795	$ 582,647
Residential Portfolio Segment [Member] | Conventional Loan [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	256,497	265,746
Financing Receivable Modifications Recorded Investment Nonaccrual Status	54,866	50,903
Financing Receivable, Troubled Debt Restructuring	311,363	316,649
Commercial Portfolio Segment [Member] | Construction Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	3,200	3,238
Financing Receivable Modifications Recorded Investment Nonaccrual Status	1,075	1,083
Financing Receivable, Troubled Debt Restructuring	4,275	4,321
Commercial Portfolio Segment [Member] | Mortgage Receivable [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	50,672	51,062
Financing Receivable Modifications Recorded Investment Nonaccrual Status	23,660	23,917
Financing Receivable, Troubled Debt Restructuring	74,332	74,979
Commercial Portfolio Segment [Member] | Commercial And Industrial Sector [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	73,531	59,689
Financing Receivable Modifications Recorded Investment Nonaccrual Status	9,188	7,160
Financing Receivable, Troubled Debt Restructuring	82,719	66,849
Consumer Portfolio Segment [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring	24,600
Consumer Portfolio Segment [Member] | Auto loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	8,021	8,556
Financing Receivable Modifications Recorded Investment Nonaccrual Status	6,165	5,984
Financing Receivable, Troubled Debt Restructuring	14,186	14,540
Consumer Portfolio Segment [Member] | Finance Leases [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	1,544	1,502
Financing Receivable Modifications Recorded Investment Nonaccrual Status	7	30
Financing Receivable, Troubled Debt Restructuring	1,551	1,532
Consumer Portfolio Segment [Member] | Personal Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	1,052	1,052
Financing Receivable Modifications Recorded Investment Nonaccrual Status	22	21
Financing Receivable, Troubled Debt Restructuring	1,074	1,073
Consumer Portfolio Segment [Member] | Other Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	4,332	4,621
Financing Receivable Modifications Recorded Investment Nonaccrual Status	709	642
Financing Receivable, Troubled Debt Restructuring	5,041	5,263
Consumer Portfolio Segment [Member] | Credit cards [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	2,754	2,791
Financing Receivable Modifications Recorded Investment Nonaccrual Status	0	0
Financing Receivable, Troubled Debt Restructuring	2,754	2,791
Puerto Rico and Virgin Islands regions [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	391,950	388,388
Financing Receivable Modifications Recorded Investment Nonaccrual Status	95,303	89,388
Financing Receivable, Troubled Debt Restructuring	487,253	477,776
Puerto Rico and Virgin Islands regions [Member] | Residential Portfolio Segment [Member] | Conventional Loan [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	253,077	262,244
Financing Receivable Modifications Recorded Investment Nonaccrual Status	54,806	50,903
Financing Receivable, Troubled Debt Restructuring	307,883	313,147
Puerto Rico and Virgin Islands regions [Member] | Commercial Portfolio Segment [Member] | Construction Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	3,200	3,238
Financing Receivable Modifications Recorded Investment Nonaccrual Status	1,075	1,083
Financing Receivable, Troubled Debt Restructuring	4,275	4,321
Puerto Rico and Virgin Islands regions [Member] | Commercial Portfolio Segment [Member] | Mortgage Receivable [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	45,193	45,534
Financing Receivable Modifications Recorded Investment Nonaccrual Status	23,660	23,917
Financing Receivable, Troubled Debt Restructuring	68,853	69,451
Puerto Rico and Virgin Islands regions [Member] | Commercial Portfolio Segment [Member] | Commercial And Industrial Sector [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	73,531	59,689
Financing Receivable Modifications Recorded Investment Nonaccrual Status	8,896	6,845
Financing Receivable, Troubled Debt Restructuring	82,427	66,534
Puerto Rico and Virgin Islands regions [Member] | Consumer Portfolio Segment [Member] | Auto loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	7,928	8,440
Financing Receivable Modifications Recorded Investment Nonaccrual Status	6,165	5,984
Financing Receivable, Troubled Debt Restructuring	14,093	14,424
Puerto Rico and Virgin Islands regions [Member] | Consumer Portfolio Segment [Member] | Finance Leases [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	1,544	1,502
Financing Receivable Modifications Recorded Investment Nonaccrual Status	7	30
Financing Receivable, Troubled Debt Restructuring	1,551	1,532
Puerto Rico and Virgin Islands regions [Member] | Consumer Portfolio Segment [Member] | Personal Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	1,052	1,052
Financing Receivable Modifications Recorded Investment Nonaccrual Status	22	21
Financing Receivable, Troubled Debt Restructuring	1,074	1,073
Puerto Rico and Virgin Islands regions [Member] | Consumer Portfolio Segment [Member] | Other Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	3,671	3,898
Financing Receivable Modifications Recorded Investment Nonaccrual Status	672	605
Financing Receivable, Troubled Debt Restructuring	4,343	4,503
Puerto Rico and Virgin Islands regions [Member] | Consumer Portfolio Segment [Member] | Credit cards [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	2,754	2,791
Financing Receivable Modifications Recorded Investment Nonaccrual Status	0	0
Financing Receivable, Troubled Debt Restructuring	2,754	2,791
Florida region
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	9,653	9,869
Financing Receivable Modifications Recorded Investment Nonaccrual Status	389	352
Financing Receivable, Troubled Debt Restructuring	10,042	10,221
Florida region | Residential Portfolio Segment [Member] | Conventional Loan [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	3,420	3,502
Financing Receivable Modifications Recorded Investment Nonaccrual Status	60	0
Financing Receivable, Troubled Debt Restructuring	3,480	3,502
Florida region | Commercial Portfolio Segment [Member] | Construction Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	0	0
Financing Receivable Modifications Recorded Investment Nonaccrual Status	0	0
Financing Receivable, Troubled Debt Restructuring	0	0
Florida region | Commercial Portfolio Segment [Member] | Mortgage Receivable [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	5,479	5,528
Financing Receivable Modifications Recorded Investment Nonaccrual Status	0	0
Financing Receivable, Troubled Debt Restructuring	5,479	5,528
Florida region | Commercial Portfolio Segment [Member] | Commercial And Industrial Sector [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	0	0
Financing Receivable Modifications Recorded Investment Nonaccrual Status	292	315
Financing Receivable, Troubled Debt Restructuring	292	315
Florida region | Consumer Portfolio Segment [Member] | Auto loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	93	116
Financing Receivable Modifications Recorded Investment Nonaccrual Status	0	0
Financing Receivable, Troubled Debt Restructuring	93	116
Florida region | Consumer Portfolio Segment [Member] | Finance Leases [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	0	0
Financing Receivable Modifications Recorded Investment Nonaccrual Status	0	0
Financing Receivable, Troubled Debt Restructuring	0	0
Florida region | Consumer Portfolio Segment [Member] | Personal Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	0	0
Financing Receivable Modifications Recorded Investment Nonaccrual Status	0	0
Financing Receivable, Troubled Debt Restructuring	0	0
Florida region | Consumer Portfolio Segment [Member] | Other Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	661	723
Financing Receivable Modifications Recorded Investment Nonaccrual Status	37	37
Financing Receivable, Troubled Debt Restructuring	698	760
Florida region | Consumer Portfolio Segment [Member] | Credit cards [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	0	0
Financing Receivable Modifications Recorded Investment Nonaccrual Status	0	0
Financing Receivable, Troubled Debt Restructuring	$ 0	$ 0