LOANS HELD FOR INVESTMENT - Corporation's nonaccrual status and loans 90 days or more still accruing (Parenthetical) (Detail) - Loans held for investmet [Member] - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 9,038,947	$ 9,002,205
Financing Receivable, 90 Days or More Past Due, Still Accruing	131,441	135,042
PCD loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, before Allowance for Credit Loss	134,000	136,700
Financing Receivable, 90 Days or More Past Due, Still Accruing	25,400	27,000
Puerto Rico and Virgin Islands regions [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, before Allowance for Credit Loss	7,103,906	7,128,277
Financing Receivable, 90 Days or More Past Due, Still Accruing	130,729	134,913
Puerto Rico and Virgin Islands regions [Member] | PCD loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, before Allowance for Credit Loss	134,000	136,700
Financing Receivable, 90 Days or More Past Due, Still Accruing	25,400	27,000
Florida region [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,935,041	1,873,928
Financing Receivable, 90 Days or More Past Due, Still Accruing	712	129
Accrual Status [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring	401,600	398,300
Accrual Status [Member] | Puerto Rico and Virgin Islands regions [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring	391,900	388,400
Accrual Status [Member] | Florida region [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring	$ 9,700	$ 9,900