LOANS HELD FOR INVESTMENT - Corporation's Aging of Loans Held for Investment Portfolio (Parenthetical) (Detail) - USD ($)	Mar. 31, 2024	Dec. 31, 2023
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans with No ACL	$ 11,662,000	$ 6,953,000
Loans Past Due 90 days or more and Still Accruing	57,515,000	59,452,000
Nonaccrual	92,965,000	83,707,000
Loans held for investment	12,311,448,000	12,185,483,000
PCD loans [Member]
Financing Receivable, Past Due [Line Items]
Loans Past Due 90 days or more and Still Accruing	8,600,000	8,300,000
Florida region [Member}
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans with No ACL	0
Nonaccrual	19,000,000.0	8,000,000.0
Loans held for investment	2,103,118,000	2,022,261,000
30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment	80,710,000	89,185,000
Residential Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment	2,801,587,000	2,821,726,000
Residential Portfolio Segment [Member] | Performing Financial Instruments [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment	2,768,902,000	2,789,487,000
Residential Portfolio Segment [Member] | Florida region [Member}
Financing Receivable, Past Due [Line Items]
Loans held for investment	474,347,000	465,720,000
Residential Portfolio Segment [Member] | Florida region [Member} | Performing Financial Instruments [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment	465,876,000	458,493,000
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member]
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans with No ACL	1,700,000	1,742,000
Loans Past Due 90 days or more and Still Accruing	10,304,000	11,029,000
Nonaccrual	32,685,000	32,239,000
Loans held for investment	2,701,932,000	2,721,490,000
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | Performing Financial Instruments [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment	2,669,247,000	2,689,251,000
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	7,700,000	7,400,000
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | Florida region [Member}
Financing Receivable, Past Due [Line Items]
Loans held for investment	473,646,000	464,777,000
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	465,175,000	457,550,000
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	72,700,000	69,900,000
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	28,265,000	29,312,000
Nonaccrual	0	0
Loans held for investment	99,655,000	100,236,000
Residential Portfolio Segment [Member] | FHA/VA government-guaranteed loans [Member] | Performing Financial Instruments [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment	99,655,000	100,236,000
Residential Portfolio Segment [Member] | FHA/VA government-guaranteed loans [Member] | Florida region [Member}
Financing Receivable, Past Due [Line Items]
Loans held for investment	701,000	943,000
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	701,000	943,000
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	7,400,000	8,200,000
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	8,800,000	7,900,000
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	13,700,000	15,400,000
Commercial Portfolio Segment [Member] | Commercial And Industrial Sector [Member]
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans with No ACL	1,644,000	1,687,000
Loans Past Due 90 days or more and Still Accruing	7,829,000	8,455,000
Nonaccrual	25,067,000	15,250,000
Loans held for investment	3,230,995,000	3,174,232,000
Commercial Portfolio Segment [Member] | Florida region [Member} | Commercial And Industrial Sector [Member]
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans with No ACL		0
Loans held for investment	940,996,000	924,824,000
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	3,134,000	1,130,000
Commercial Portfolio Segment [Member] | Mortgage Receivable [Member]
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans with No ACL	6,865,000	2,536,000
Loans Past Due 90 days or more and Still Accruing	939,000	1,108,000
Nonaccrual	11,976,000	12,205,000
Loans held for investment	2,361,731,000	2,317,083,000
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	900,000
Commercial Portfolio Segment [Member] | Mortgage Receivable [Member] | Florida region [Member}
Financing Receivable, Past Due [Line Items]
Loans held for investment	592,484,000	526,446,000
Commercial Portfolio Segment [Member] | Mortgage Receivable [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment	708,000	17,000
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	1,900,000	1,100,000
Commercial Portfolio Segment [Member] | Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans with No ACL	971,000	972,000
Loans Past Due 90 days or more and Still Accruing	2,284,000	2,297,000
Nonaccrual	1,498,000	1,569,000
Loans held for investment	237,288,000	214,777,000
Commercial Portfolio Segment [Member] | Construction Loans [Member] | Florida region [Member}
Financing Receivable, Past Due [Line Items]
Loans held for investment	89,664,000	99,376,000
Commercial Portfolio Segment [Member] | Construction Loans [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment	$ 0	$ 0