LOANS HELD FOR INVESTMENT - Corporation's Aging of Loans Held for Investment Portfolio (Parenthetical) (Detail) - USD ($)	Sep. 30, 2023	Dec. 31, 2022
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans with No ACL	$ 9,967,000	$ 25,026,000
Loans Past Due 90 days or more and Still Accruing	62,892,000	80,283,000
Nonaccrual	93,164,000	89,935,000
Loans held for investment	11,950,932,000	11,552,825,000
PCD loans [Member]
Financing Receivable, Past Due [Line Items]
Loans Past Due 90 days or more and Still Accruing	8,900,000	12,000,000.0
Florida region [Member}
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans with No ACL	0
Nonaccrual	8,700,000	8,300,000
Loans held for investment	2,044,643,000	2,088,351,000
30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment	79,051,000	58,718,000
Residential Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment	2,812,631,000	2,847,290,000
Residential Portfolio Segment [Member] | Performing Financial Instruments [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment	2,780,685,000	2,804,518,000
Residential Portfolio Segment [Member] | Florida region [Member}
Financing Receivable, Past Due [Line Items]
Loans held for investment	458,952,000	429,390,000
Residential Portfolio Segment [Member] | Florida region [Member} | Performing Financial Instruments [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment	452,255,000	422,089,000
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member]
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans with No ACL	1,910,000	2,292,000
Loans Past Due 90 days or more and Still Accruing	11,958,000	16,821,000
Nonaccrual	31,946,000	42,772,000
Loans held for investment	2,708,535,000	2,729,132,000
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | Performing Financial Instruments [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment	2,676,589,000	2,686,360,000
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	8,000,000.0	11,000,000.0
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | Florida region [Member}
Financing Receivable, Past Due [Line Items]
Loans held for investment	457,988,000	428,648,000
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | Florida region [Member} | Performing Financial Instruments [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment	451,291,000	421,347,000
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment	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]
Loans held for investment	65,500,000	65,200,000
Residential Portfolio Segment [Member] | FHA/VA government-guaranteed loans [Member]
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans with No ACL	0	0
Loans Past Due 90 days or more and Still Accruing	32,167,000	48,456,000
Nonaccrual	0	0
Loans held for investment	104,096,000	118,158,000
Residential Portfolio Segment [Member] | FHA/VA government-guaranteed loans [Member] | Performing Financial Instruments [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment	104,096,000	118,158,000
Residential Portfolio Segment [Member] | FHA/VA government-guaranteed loans [Member] | Florida region [Member}
Financing Receivable, Past Due [Line Items]
Loans held for investment	964,000	742,000
Residential Portfolio Segment [Member] | FHA/VA government-guaranteed loans [Member] | Florida region [Member} | Performing Financial Instruments [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment	964,000	742,000
Residential Portfolio Segment [Member] | FHA/VA government-guaranteed loans [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment	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]
Loans held for investment	6,900,000	6,100,000
Residential Portfolio Segment [Member] | GNMA [Member] | Repurchase Option Program [Member]
Financing Receivable, Past Due [Line Items]
Loans Past Due 90 days or more and Still Accruing	8,500,000	10,300,000
Residential Portfolio Segment [Member] | Federal Housing Administration Loan [Member] | Past Due, 15 Months Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Loans Past Due 90 days or more and Still Accruing	17,400,000	28,200,000
Commercial Portfolio Segment [Member] | Commercial And Industrial Sector [Member]
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans with No ACL	1,523,000	3,300,000
Loans Past Due 90 days or more and Still Accruing	10,749,000	6,332,000
Nonaccrual	18,809,000	7,830,000
Loans held for investment	3,030,954,000	2,886,263,000
Commercial Portfolio Segment [Member] | Florida region [Member} | Commercial And Industrial Sector [Member]
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans with No ACL		300,000
Loans held for investment	942,680,000	1,026,154,000
Commercial Portfolio Segment [Member] | 30-59 Days Past Due [Member] | Commercial And Industrial Sector [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment	441,000	1,984,000
Commercial Portfolio Segment [Member] | Mortgage Receivable [Member]
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans with No ACL	5,458,000	15,991,000
Loans Past Due 90 days or more and Still Accruing	2,373,000	3,771,000
Nonaccrual	21,632,000	22,319,000
Loans held for investment	2,316,113,000	2,358,851,000
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	900,000	1,000,000.0
Commercial Portfolio Segment [Member] | Mortgage Receivable [Member] | Florida region [Member}
Financing Receivable, Past Due [Line Items]
Loans held for investment	536,105,000	524,647,000
Commercial Portfolio Segment [Member] | Mortgage Receivable [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment	930,000	300,000
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]
Loans held for investment	1,000,000.0	1,600,000
Commercial Portfolio Segment [Member] | Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans with No ACL	973,000	977,000
Loans Past Due 90 days or more and Still Accruing	7,000	128,000
Nonaccrual	1,640,000	2,208,000
Loans held for investment	202,774,000	132,953,000
Commercial Portfolio Segment [Member] | Construction Loans [Member] | Florida region [Member}
Financing Receivable, Past Due [Line Items]
Loans held for investment	100,447,000	98,181,000
Commercial Portfolio Segment [Member] | Construction Loans [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment	1,834,000	$ 0
Commercial Portfolio Segment [Member] | Construction Loans [Member] | 30-59 Days Past Due [Member] | Less Than Two Payments In Arrears [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment	$ 100,000