LOANS HELD FOR INVESTMENT - Breakdown Between Accrual and Nonaccrual Status of TDRs (Detail) - TDR [Member] - USD ($) $ in Thousands	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Financing Receivable Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	$ 399,672		$ 398,257
Financing Receivable Modifications Recorded Investment Nonaccrual	88,943		89,740
Financing Receivable, Troubled Debt Restructuring	488,615	$ 496,207	487,997	$ 495,838	$ 582,389	$ 582,647
Residential Portfolio Segment [Member] | Conventional Loan [Member]
Financing Receivable Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	257,582		265,746
Financing Receivable Modifications Recorded Investment Nonaccrual	54,656		50,903
Financing Receivable, Troubled Debt Restructuring	312,238		316,649
Commercial Portfolio Segment [Member] | Construction Loans [Member]
Financing Receivable Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	2,542		3,238
Financing Receivable Modifications Recorded Investment Nonaccrual	952		1,083
Financing Receivable, Troubled Debt Restructuring	3,494		4,321
Commercial Portfolio Segment [Member] | Mortgage Receivable [Member]
Financing Receivable Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	49,150		51,062
Financing Receivable Modifications Recorded Investment Nonaccrual	18,450		23,917
Financing Receivable, Troubled Debt Restructuring	67,600		74,979
Commercial Portfolio Segment [Member] | Commercial And Industrial Sector [Member]
Financing Receivable Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	74,390		59,689
Financing Receivable Modifications Recorded Investment Nonaccrual	9,127		7,160
Financing Receivable, Troubled Debt Restructuring	83,517		66,849
Consumer Portfolio Segment [Member]
Financing Receivable Modifications [Line Items]
Financing Receivable, Troubled Debt Restructuring	21,800
Consumer Portfolio Segment [Member] | Auto loans [Member]
Financing Receivable Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	7,062		8,556
Financing Receivable Modifications Recorded Investment Nonaccrual	5,282		5,984
Financing Receivable, Troubled Debt Restructuring	12,344		14,540
Consumer Portfolio Segment [Member] | Finance Leases [Member]
Financing Receivable Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	1,340		1,502
Financing Receivable Modifications Recorded Investment Nonaccrual	8		30
Financing Receivable, Troubled Debt Restructuring	1,348		1,532
Consumer Portfolio Segment [Member] | Personal Loans [Member]
Financing Receivable Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	960		1,052
Financing Receivable Modifications Recorded Investment Nonaccrual	0		21
Financing Receivable, Troubled Debt Restructuring	960		1,073
Consumer Portfolio Segment [Member] | Other Loans [Member]
Financing Receivable Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	4,080		4,621
Financing Receivable Modifications Recorded Investment Nonaccrual	468		642
Financing Receivable, Troubled Debt Restructuring	4,548		5,263
Consumer Portfolio Segment [Member] | Credit cards [Member]
Financing Receivable Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	2,566		2,791
Financing Receivable Modifications Recorded Investment Nonaccrual	0		0
Financing Receivable, Troubled Debt Restructuring	2,566		2,791
PR And VI [Member]
Financing Receivable Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	390,123		388,388
Financing Receivable Modifications Recorded Investment Nonaccrual	88,659		89,388
Financing Receivable, Troubled Debt Restructuring	478,782		477,776
PR And VI [Member] | Residential Portfolio Segment [Member] | Conventional Loan [Member]
Financing Receivable Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	254,199		262,244
Financing Receivable Modifications Recorded Investment Nonaccrual	54,656		50,903
Financing Receivable, Troubled Debt Restructuring	308,855		313,147
PR And VI [Member] | Commercial Portfolio Segment [Member] | Construction Loans [Member]
Financing Receivable Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	2,542		3,238
Financing Receivable Modifications Recorded Investment Nonaccrual	952		1,083
Financing Receivable, Troubled Debt Restructuring	3,494		4,321
PR And VI [Member] | Commercial Portfolio Segment [Member] | Mortgage Receivable [Member]
Financing Receivable Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	43,646		45,534
Financing Receivable Modifications Recorded Investment Nonaccrual	18,450		23,917
Financing Receivable, Troubled Debt Restructuring	62,096		69,451
PR And VI [Member] | Commercial Portfolio Segment [Member] | Commercial And Industrial Sector [Member]
Financing Receivable Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	74,390		59,689
Financing Receivable Modifications Recorded Investment Nonaccrual	8,880		6,845
Financing Receivable, Troubled Debt Restructuring	83,270		66,534
PR And VI [Member] | Consumer Portfolio Segment [Member] | Auto loans [Member]
Financing Receivable Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	6,983		8,440
Financing Receivable Modifications Recorded Investment Nonaccrual	5,282		5,984
Financing Receivable, Troubled Debt Restructuring	12,265		14,424
PR And VI [Member] | Consumer Portfolio Segment [Member] | Finance Leases [Member]
Financing Receivable Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	1,340		1,502
Financing Receivable Modifications Recorded Investment Nonaccrual	8		30
Financing Receivable, Troubled Debt Restructuring	1,348		1,532
PR And VI [Member] | Consumer Portfolio Segment [Member] | Personal Loans [Member]
Financing Receivable Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	960		1,052
Financing Receivable Modifications Recorded Investment Nonaccrual	0		21
Financing Receivable, Troubled Debt Restructuring	960		1,073
PR And VI [Member] | Consumer Portfolio Segment [Member] | Other Loans [Member]
Financing Receivable Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	3,497		3,898
Financing Receivable Modifications Recorded Investment Nonaccrual	431		605
Financing Receivable, Troubled Debt Restructuring	3,928		4,503
PR And VI [Member] | Consumer Portfolio Segment [Member] | Credit cards [Member]
Financing Receivable Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	2,566		2,791
Financing Receivable Modifications Recorded Investment Nonaccrual	0		0
Financing Receivable, Troubled Debt Restructuring	2,566		2,791
FL
Financing Receivable Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	9,549		9,869
Financing Receivable Modifications Recorded Investment Nonaccrual	284		352
Financing Receivable, Troubled Debt Restructuring	9,833		10,221
FL | Residential Portfolio Segment [Member] | Conventional Loan [Member]
Financing Receivable Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	3,383		3,502
Financing Receivable Modifications Recorded Investment Nonaccrual	0		0
Financing Receivable, Troubled Debt Restructuring	3,383		3,502
FL | Commercial Portfolio Segment [Member] | Construction Loans [Member]
Financing Receivable Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	0		0
Financing Receivable Modifications Recorded Investment Nonaccrual	0		0
Financing Receivable, Troubled Debt Restructuring	0		0
FL | Commercial Portfolio Segment [Member] | Mortgage Receivable [Member]
Financing Receivable Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	5,504		5,528
Financing Receivable Modifications Recorded Investment Nonaccrual	0		0
Financing Receivable, Troubled Debt Restructuring	5,504		5,528
FL | Commercial Portfolio Segment [Member] | Commercial And Industrial Sector [Member]
Financing Receivable Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	0		0
Financing Receivable Modifications Recorded Investment Nonaccrual	247		315
Financing Receivable, Troubled Debt Restructuring	247		315
FL | Consumer Portfolio Segment [Member] | Auto loans [Member]
Financing Receivable Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	79		116
Financing Receivable Modifications Recorded Investment Nonaccrual	0		0
Financing Receivable, Troubled Debt Restructuring	79		116
FL | Consumer Portfolio Segment [Member] | Finance Leases [Member]
Financing Receivable Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	0		0
Financing Receivable Modifications Recorded Investment Nonaccrual	0		0
Financing Receivable, Troubled Debt Restructuring	0		0
FL | Consumer Portfolio Segment [Member] | Personal Loans [Member]
Financing Receivable Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	0		0
Financing Receivable Modifications Recorded Investment Nonaccrual	0		0
Financing Receivable, Troubled Debt Restructuring	0		0
FL | Consumer Portfolio Segment [Member] | Other Loans [Member]
Financing Receivable Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	583		723
Financing Receivable Modifications Recorded Investment Nonaccrual	37		37
Financing Receivable, Troubled Debt Restructuring	620		760
FL | Consumer Portfolio Segment [Member] | Credit cards [Member]
Financing Receivable Modifications [Line Items]
Financing Receivable Modifications Recorded Investment Accrual Status	0		0
Financing Receivable Modifications Recorded Investment Nonaccrual	0		0
Financing Receivable, Troubled Debt Restructuring	$ 0		$ 0