LOANS HELD FOR INVESTMENT - Corporation's Residential Mortgage Loans by Origination Year Based on Original Credit Score (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 11,140,582	$ 11,777,289
Puerto Rico and Virgin Islands regions [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	9,150,483	9,788,106
Florida region [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,990,099	1,989,183
Residential Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	91,132
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	73,910
Financing Receivable, Originated Two Years before Latest Fiscal Year	108,810
Financing Receivable, Originated Three Years before Latest Fiscal Year	145,944
Financing Receivable, Originated Four Years before Latest Fiscal Year	135,486
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	2,539,733
Financing Receivable, Revolving	0
Financing Receivable, before Allowance for Credit Loss	3,095,015	3,521,954
Residential Portfolio Segment [Member] | Puerto Rico and Virgin Islands regions [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	51,211
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	35,549
Financing Receivable, Originated Two Years before Latest Fiscal Year	62,409
Financing Receivable, Originated Three Years before Latest Fiscal Year	92,201
Financing Receivable, Originated Four Years before Latest Fiscal Year	69,713
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	2,330,080
Financing Receivable, Revolving	0
Financing Receivable, before Allowance for Credit Loss	2,641,163	3,002,203
Residential Portfolio Segment [Member] | Florida region [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	39,921
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	38,361
Financing Receivable, Originated Two Years before Latest Fiscal Year	46,401
Financing Receivable, Originated Three Years before Latest Fiscal Year	53,743
Financing Receivable, Originated Four Years before Latest Fiscal Year	65,773
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	209,653
Financing Receivable, Revolving	0
Financing Receivable, before Allowance for Credit Loss	453,852	519,751
Residential Portfolio Segment [Member] | Loans Insured or Guaranteed by US Government Authorities [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	359
Financing Receivable, Originated Two Years before Latest Fiscal Year	1,090
Financing Receivable, Originated Three Years before Latest Fiscal Year	2,168
Financing Receivable, Originated Four Years before Latest Fiscal Year	4,134
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	126,534
Financing Receivable, Revolving	0
Financing Receivable, before Allowance for Credit Loss	134,285	150,734
Residential Portfolio Segment [Member] | Loans Insured or Guaranteed by US Government Authorities [Member] | Puerto Rico and Virgin Islands regions [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	359
Financing Receivable, Originated Two Years before Latest Fiscal Year	1,090
Financing Receivable, Originated Three Years before Latest Fiscal Year	2,168
Financing Receivable, Originated Four Years before Latest Fiscal Year	4,134
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	125,661
Financing Receivable, Revolving	0
Financing Receivable, before Allowance for Credit Loss	133,412	149,564
Residential Portfolio Segment [Member] | Loans Insured or Guaranteed by US Government Authorities [Member] | Florida region [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0
Financing Receivable, Originated Two Years before Latest Fiscal Year	0
Financing Receivable, Originated Three Years before Latest Fiscal Year	0
Financing Receivable, Originated Four Years before Latest Fiscal Year	0
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	873
Financing Receivable, Revolving	0
Financing Receivable, before Allowance for Credit Loss	873	1,170
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,960,730	3,371,220
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | Puerto Rico and Virgin Islands regions [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,507,751	2,852,639
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | Florida region [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss	452,979	518,581
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | FICO Score Less than 620 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	42
Financing Receivable, Originated Two Years before Latest Fiscal Year	76
Financing Receivable, Originated Three Years before Latest Fiscal Year	2,513
Financing Receivable, Originated Four Years before Latest Fiscal Year	52
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	285,044
Financing Receivable, Revolving	0
Financing Receivable, before Allowance for Credit Loss	287,727	329,520
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | FICO Score Less than 620 [Member] | Puerto Rico and Virgin Islands regions [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	42
Financing Receivable, Originated Two Years before Latest Fiscal Year	76
Financing Receivable, Originated Three Years before Latest Fiscal Year	459
Financing Receivable, Originated Four Years before Latest Fiscal Year	52
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	284,532
Financing Receivable, Revolving	0
Financing Receivable, before Allowance for Credit Loss	285,161	326,190
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | FICO Score Less than 620 [Member] | Florida region [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0
Financing Receivable, Originated Two Years before Latest Fiscal Year	0
Financing Receivable, Originated Three Years before Latest Fiscal Year	2,054
Financing Receivable, Originated Four Years before Latest Fiscal Year	0
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	512
Financing Receivable, Revolving	0
Financing Receivable, before Allowance for Credit Loss	2,566	3,330
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | FICO Score Greater than or equal to 620 and less than 680 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	6,042
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	4,923
Financing Receivable, Originated Two Years before Latest Fiscal Year	6,753
Financing Receivable, Originated Three Years before Latest Fiscal Year	8,162
Financing Receivable, Originated Four Years before Latest Fiscal Year	13,403
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	476,598
Financing Receivable, Revolving	0
Financing Receivable, before Allowance for Credit Loss	515,881	589,729
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | FICO Score Greater than or equal to 620 and less than 680 [Member] | Puerto Rico and Virgin Islands regions [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	2,232
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	1,374
Financing Receivable, Originated Two Years before Latest Fiscal Year	2,529
Financing Receivable, Originated Three Years before Latest Fiscal Year	5,537
Financing Receivable, Originated Four Years before Latest Fiscal Year	6,312
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	453,544
Financing Receivable, Revolving	0
Financing Receivable, before Allowance for Credit Loss	471,528	541,309
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | FICO Score Greater than or equal to 620 and less than 680 [Member] | Florida region [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	3,810
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	3,549
Financing Receivable, Originated Two Years before Latest Fiscal Year	4,224
Financing Receivable, Originated Three Years before Latest Fiscal Year	2,625
Financing Receivable, Originated Four Years before Latest Fiscal Year	7,091
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	23,054
Financing Receivable, Revolving	0
Financing Receivable, before Allowance for Credit Loss	44,353	48,420
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | FICO Score Greater than or equal to 680 and less than 740 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	26,597
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	24,578
Financing Receivable, Originated Two Years before Latest Fiscal Year	36,258
Financing Receivable, Originated Three Years before Latest Fiscal Year	45,686
Financing Receivable, Originated Four Years before Latest Fiscal Year	41,174
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	686,664
Financing Receivable, Revolving	0
Financing Receivable, before Allowance for Credit Loss	860,957	980,994
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | FICO Score Greater than or equal to 680 and less than 740 [Member] | Puerto Rico and Virgin Islands regions [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	13,493
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	13,862
Financing Receivable, Originated Two Years before Latest Fiscal Year	23,139
Financing Receivable, Originated Three Years before Latest Fiscal Year	33,794
Financing Receivable, Originated Four Years before Latest Fiscal Year	22,308
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	636,765
Financing Receivable, Revolving	0
Financing Receivable, before Allowance for Credit Loss	743,361	841,797
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | FICO Score Greater than or equal to 680 and less than 740 [Member] | Florida region [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	13,104
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	10,716
Financing Receivable, Originated Two Years before Latest Fiscal Year	13,119
Financing Receivable, Originated Three Years before Latest Fiscal Year	11,892
Financing Receivable, Originated Four Years before Latest Fiscal Year	18,866
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	49,899
Financing Receivable, Revolving	0
Financing Receivable, before Allowance for Credit Loss	117,596	139,197
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | FICO Score Greater than or equal to 740 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	58,493
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	44,008
Financing Receivable, Originated Two Years before Latest Fiscal Year	64,633
Financing Receivable, Originated Three Years before Latest Fiscal Year	87,415
Financing Receivable, Originated Four Years before Latest Fiscal Year	76,723
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	964,893
Financing Receivable, Revolving	0
Financing Receivable, before Allowance for Credit Loss	1,296,165	1,470,977
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | FICO Score Greater than or equal to 740 [Member] | Puerto Rico and Virgin Islands regions [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	35,486
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	19,912
Financing Receivable, Originated Two Years before Latest Fiscal Year	35,575
Financing Receivable, Originated Three Years before Latest Fiscal Year	50,243
Financing Receivable, Originated Four Years before Latest Fiscal Year	36,907
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	829,578
Financing Receivable, Revolving	0
Financing Receivable, before Allowance for Credit Loss	1,007,701	1,143,343
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | FICO Score Greater than or equal to 740 [Member] | Florida region [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	23,007
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	24,096
Financing Receivable, Originated Two Years before Latest Fiscal Year	29,058
Financing Receivable, Originated Three Years before Latest Fiscal Year	37,172
Financing Receivable, Originated Four Years before Latest Fiscal Year	39,816
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	135,315
Financing Receivable, Revolving	0
Financing Receivable, before Allowance for Credit Loss	$ 288,464	$ 327,634