LOANS HELD FOR INVESTMENT - Corporation's Aging of Loans Held for Investment Portfolio (Parenthetical) (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
Current	$ 11,278,986,000	$ 8,493,827,000
Financing Receivable, Past Due	498,303,000	508,378,000
Loans held for investment	11,777,289,000	9,002,205,000
Puerto Rico and Virgin Islands regions [Member]
Financing Receivable, Past Due [Line Items]
Current	9,310,380,000	6,639,398,000
Financing Receivable, Past Due	477,726,000	488,879,000
Loans held for investment	9,788,106,000	7,128,277,000
Florida region [Member}
Financing Receivable, Past Due [Line Items]
Current	1,968,606,000	1,854,429,000
Financing Receivable, Past Due	20,577,000	19,499,000
Loans held for investment	1,989,183,000	1,873,928,000
30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	48,129,000	55,640,000
30-59 Days Past Due [Member] | Puerto Rico and Virgin Islands regions [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	47,143,000	53,892,000
30-59 Days Past Due [Member] | Florida region [Member}
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	$ 986,000	1,748,000
Residential Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Threshold Period Past Due, Writeoff	180 days
Loans held for investment	$ 3,521,954,000	2,933,773,000
Residential Portfolio Segment [Member] | Puerto Rico and Virgin Islands regions [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment	3,002,203,000	2,367,587,000
Residential Portfolio Segment [Member] | Florida region [Member}
Financing Receivable, Past Due [Line Items]
Loans held for investment	519,751,000	566,186,000
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member]
Financing Receivable, Past Due [Line Items]
Current	3,142,742,000	2,562,747,000
Financing Receivable, Past Due	228,478,000	247,117,000
Loans held for investment	3,371,220,000	2,809,864,000
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | Puerto Rico and Virgin Islands regions [Member]
Financing Receivable, Past Due [Line Items]
Current	2,641,820,000	2,013,525,000
Financing Receivable, Past Due	210,819,000	231,633,000
Loans held for investment	2,852,639,000	2,245,158,000
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | Florida region [Member}
Financing Receivable, Past Due [Line Items]
Current	500,922,000	549,222,000
Financing Receivable, Past Due	17,659,000	15,484,000
Loans held for investment	518,581,000	564,706,000
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	0	0
Loans held for investment	111,800,000	116,200,000
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | 30-59 Days Past Due [Member] | Puerto Rico and Virgin Islands regions [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	0	0
Loans held for investment	105,200,000	110,500,000
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | 30-59 Days Past Due [Member] | Florida region [Member}
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	0	0
Loans held for investment	6,600,000	5,800,000
Residential Portfolio Segment [Member] | FHA/VA government-guaranteed loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, 15 Months or More Past Due, No Still Accruing	$ 57,900,000	$ 37,900,000
Period of residential mortgage loan that are no longer accruing interest	15 months	15 months
Current	$ 49,268,000	$ 40,701,000
Financing Receivable, Past Due	101,466,000	83,208,000
Loans held for investment	150,734,000	123,909,000
Residential Portfolio Segment [Member] | FHA/VA government-guaranteed loans [Member] | Puerto Rico and Virgin Islands regions [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, 15 Months or More Past Due, No Still Accruing	$ 57,900,000	$ 37,900,000
Period of residential mortgage loan that are no longer accruing interest	15 months	15 months
Current	$ 48,348,000	$ 39,350,000
Financing Receivable, Past Due	101,216,000	83,079,000
Loans held for investment	149,564,000	122,429,000
Residential Portfolio Segment [Member] | FHA/VA government-guaranteed loans [Member] | Florida region [Member}
Financing Receivable, Past Due [Line Items]
Financing Receivable, 15 Months or More Past Due, No Still Accruing	$ 0	$ 0
Period of residential mortgage loan that are no longer accruing interest	15 months	15 months
Current	$ 920,000	$ 1,351,000
Financing Receivable, Past Due	250,000	129,000
Loans held for investment	1,170,000	1,480,000
Residential Portfolio Segment [Member] | FHA/VA government-guaranteed loans [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	0	0
Loans held for investment	6,100,000	7,100,000
Residential Portfolio Segment [Member] | FHA/VA government-guaranteed loans [Member] | 30-59 Days Past Due [Member] | Puerto Rico and Virgin Islands regions [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	0	0
Loans held for investment	5,900,000	6,700,000
Residential Portfolio Segment [Member] | FHA/VA government-guaranteed loans [Member] | 30-59 Days Past Due [Member] | Florida region [Member}
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	0	0
Loans held for investment	200,000	400,000
Residential Portfolio Segment [Member] | GNMA [Member] | Repurchase Option Program [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	10,700,000	35,600,000
Residential Portfolio Segment [Member] | GNMA [Member] | Repurchase Option Program [Member] | Puerto Rico and Virgin Islands regions [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	10,700,000	35,600,000
Commercial Portfolio Segment [Member] | Mortgage Receivable [Member]
Financing Receivable, Past Due [Line Items]
Current	2,186,080,000	1,398,737,000
Financing Receivable, Past Due	44,522,000	45,849,000
Loans held for investment	2,230,602,000	1,444,586,000
Commercial Portfolio Segment [Member] | Mortgage Receivable [Member] | Puerto Rico and Virgin Islands regions [Member]
Financing Receivable, Past Due [Line Items]
Current	1,808,702,000	1,034,921,000
Financing Receivable, Past Due	44,522,000	44,979,000
Loans held for investment	1,853,224,000	1,079,900,000
Commercial Portfolio Segment [Member] | Mortgage Receivable [Member] | Florida region [Member}
Financing Receivable, Past Due [Line Items]
Current	377,378,000	363,816,000
Financing Receivable, Past Due	0	870,000
Loans held for investment	377,378,000	364,686,000
Commercial Portfolio Segment [Member] | Mortgage Receivable [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	5,071,000	0
Loans held for investment	5,000,000.0	6,600,000
Commercial Portfolio Segment [Member] | Mortgage Receivable [Member] | 30-59 Days Past Due [Member] | Puerto Rico and Virgin Islands regions [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	5,071,000	0
Loans held for investment	5,000,000.0	6,000,000.0
Commercial Portfolio Segment [Member] | Mortgage Receivable [Member] | 30-59 Days Past Due [Member] | Florida region [Member}
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	0	0
Loans held for investment		600,000
Commercial Portfolio Segment [Member] | Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Current	199,510,000	101,430,000
Financing Receivable, Past Due	12,990,000	9,887,000
Loans held for investment	212,500,000	111,317,000
Commercial Portfolio Segment [Member] | Construction Loans [Member] | Puerto Rico and Virgin Islands regions [Member]
Financing Receivable, Past Due [Line Items]
Current	72,026,000	38,359,000
Financing Receivable, Past Due	12,990,000	9,887,000
Loans held for investment	85,016,000	48,246,000
Commercial Portfolio Segment [Member] | Construction Loans [Member] | Florida region [Member}
Financing Receivable, Past Due [Line Items]
Current	127,484,000	63,071,000
Financing Receivable, Past Due	0	0
Loans held for investment	127,484,000	63,071,000
Commercial Portfolio Segment [Member] | Construction Loans [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	0	0
Loans held for investment	100,000	100,000
Commercial Portfolio Segment [Member] | Construction Loans [Member] | 30-59 Days Past Due [Member] | Puerto Rico and Virgin Islands regions [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	0	0
Loans held for investment	100,000	100,000
Commercial Portfolio Segment [Member] | Construction Loans [Member] | 30-59 Days Past Due [Member] | Florida region [Member}
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	0	0
Consumer Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment	2,609,643,000	2,281,653,000
Consumer Portfolio Segment [Member] | Puerto Rico and Virgin Islands regions [Member]
Financing Receivable, Past Due [Line Items]
Loans held for investment	2,582,932,000	2,241,131,000
Consumer Portfolio Segment [Member] | Florida region [Member}
Financing Receivable, Past Due [Line Items]
Loans held for investment	$ 26,711,000	$ 40,522,000
Consumer Portfolio Segment [Member] | Credit Card [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Threshold Period Past Due, Writeoff	180 days	180 days
Consumer Portfolio Segment [Member] | Credit Card [Member] | Puerto Rico and Virgin Islands regions [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Threshold Period Past Due, Writeoff	180 days	180 days