LOANS HELD FOR INVESTMENT - Corporation's Aging of Loans Held for Investment Portfolio (Parenthetical) (Detail) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 11,577,985	$ 11,552,825
Nonaccrual Loans with No ACL	24,574	25,026
Loans Past Due 90 days or more and Still Accruing	74,380	80,283
Nonaccrual	89,142	89,935
PCD loans [Member]
Financing Receivable, Past Due [Line Items]
Loans Past Due 90 days or more and Still Accruing	10,400	12,000
Florida region [Member}
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,979,362	2,088,351
Nonaccrual	15,200	8,300
30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	54,822	58,718
Residential Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,811,528	2,847,290
Residential Portfolio Segment [Member] \| Performing Financial Instruments [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,775,118	2,804,518
Residential Portfolio Segment [Member] \| Florida region [Member}
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	429,746	429,390
Residential Portfolio Segment [Member] \| Florida region [Member} \| Performing Financial Instruments [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	422,329	422,089
Residential Portfolio Segment [Member] \| Conventional residential mortgage loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,699,959	2,729,132
Nonaccrual Loans with No ACL	2,250	2,292
Loans Past Due 90 days or more and Still Accruing	13,640	16,821
Nonaccrual	36,410	42,772
Residential Portfolio Segment [Member] \| Conventional residential mortgage loans [Member] \| Performing Financial Instruments [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,663,549	2,686,360
Residential Portfolio Segment [Member] \| Conventional residential mortgage loans [Member] \| PCD loans [Member]
Financing Receivable, Past Due [Line Items]
Loans Past Due 90 days or more and Still Accruing	9,400	11,000
Residential Portfolio Segment [Member] \| Conventional residential mortgage loans [Member] \| Florida region [Member}
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	429,011	428,648
Residential Portfolio Segment [Member] \| Conventional residential mortgage loans [Member] \| Florida region [Member} \| Performing Financial Instruments [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	421,594	421,347
Residential Portfolio Segment [Member] \| Conventional residential mortgage loans [Member] \| 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
Residential Portfolio Segment [Member] \| Conventional residential mortgage loans [Member] \| 30-59 Days Past Due [Member] \| Less Than Two Payments In Arrears [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	60,700	65,200
Residential Portfolio Segment [Member] \| FHA/VA government-guaranteed loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	111,569	118,158
Nonaccrual Loans with No ACL	0	0
Loans Past Due 90 days or more and Still Accruing	41,723	48,456
Nonaccrual	0	0
Residential Portfolio Segment [Member] \| FHA/VA government-guaranteed loans [Member] \| Performing Financial Instruments [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	111,569	118,158
Residential Portfolio Segment [Member] \| FHA/VA government-guaranteed loans [Member] \| Florida region [Member}
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	735	742
Residential Portfolio Segment [Member] \| FHA/VA government-guaranteed loans [Member] \| Florida region [Member} \| Performing Financial Instruments [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	735	742
Residential Portfolio Segment [Member] \| FHA/VA government-guaranteed loans [Member] \| 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
Residential Portfolio Segment [Member] \| FHA/VA government-guaranteed loans [Member] \| 30-59 Days Past Due [Member] \| Less Than Two Payments In Arrears [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	5,300	6,100
Residential Portfolio Segment [Member] \| FHA/VA government-guaranteed loans [Member] \| Past Due, 15 Months Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Loans Past Due 90 days or more and Still Accruing	25,900	28,200
Residential Portfolio Segment [Member] \| GNMA [Member] \| Repurchase Option Program [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	7,100	10,400
Loans Past Due 90 days or more and Still Accruing	7,100	10,300
Commercial Portfolio Segment [Member] \| Commercial And Industrial Sector [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,862,189	2,886,263
Nonaccrual Loans with No ACL	1,858	3,300
Loans Past Due 90 days or more and Still Accruing	6,355	6,332
Nonaccrual	13,404	7,830
Commercial Portfolio Segment [Member] \| Florida region [Member} \| Commercial And Industrial Sector [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	920,961	1,026,154
Nonaccrual Loans with No ACL	300	300
Commercial Portfolio Segment [Member] \| 30-59 Days Past Due [Member] \| Commercial And Industrial Sector [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,438	1,984
Commercial Portfolio Segment [Member] \| Mortgage Receivable [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,353,659	2,358,851
Nonaccrual Loans with No ACL	15,787	15,991
Loans Past Due 90 days or more and Still Accruing	7,929	3,771
Nonaccrual	21,598	22,319
Commercial Portfolio Segment [Member] \| Mortgage Receivable [Member] \| PCD loans [Member]
Financing Receivable, Past Due [Line Items]
Loans Past Due 90 days or more and Still Accruing	1,000	1,000
Commercial Portfolio Segment [Member] \| Mortgage Receivable [Member] \| Florida region [Member}
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	524,486	524,647
Commercial Portfolio Segment [Member] \| Mortgage Receivable [Member] \| 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	509	300
Commercial Portfolio Segment [Member] \| Mortgage Receivable [Member] \| 30-59 Days Past Due [Member] \| Less Than Two Payments In Arrears [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 1,100	$ 1,600

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