LOANS HELD FOR INVESTMENT - Corporation's Residential Mortgage Loans by Origination Year Based on Original Loan-to-Value-Ratio (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Financing Receivable Recorded Investment [Line Items]
Loans held for investment	$ 11,847,275	$ 9,002,205
Puerto Rico and Virgin Islands regions [Member]
Financing Receivable Recorded Investment [Line Items]
Loans held for investment	9,834,201	7,128,277
Florida region [Member]
Financing Receivable Recorded Investment [Line Items]
Loans held for investment	2,013,074	1,873,928
Residential Portfolio Segment [Member]
Financing Receivable Recorded Investment [Line Items]
Financing Receivable, Originated in Current Fiscal Year	59,105
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	130,248
Financing Receivable, Originated Two Years before Latest Fiscal Year	188,166
Financing Receivable, Originated Three Years before Latest Fiscal Year	179,929
Financing Receivable, Originated Four Years before Latest Fiscal Year	217,522
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	2,861,743
Financing Receivable, Revolving	0
Loans held for investment	3,636,713	2,933,773
Residential Portfolio Segment [Member] | Puerto Rico and Virgin Islands regions [Member]
Financing Receivable Recorded Investment [Line Items]
Financing Receivable, Originated in Current Fiscal Year	30,680
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	74,990
Financing Receivable, Originated Two Years before Latest Fiscal Year	121,271
Financing Receivable, Originated Three Years before Latest Fiscal Year	82,549
Financing Receivable, Originated Four Years before Latest Fiscal Year	129,927
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	2,660,942
Financing Receivable, Revolving	0
Loans held for investment	3,100,359	2,367,587
Residential Portfolio Segment [Member] | Florida region [Member]
Financing Receivable Recorded Investment [Line Items]
Financing Receivable, Originated in Current Fiscal Year	28,425
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	55,258
Financing Receivable, Originated Two Years before Latest Fiscal Year	66,895
Financing Receivable, Originated Three Years before Latest Fiscal Year	97,380
Financing Receivable, Originated Four Years before Latest Fiscal Year	87,595
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	200,801
Financing Receivable, Revolving	0
Loans held for investment	536,354	566,186
Residential Portfolio Segment [Member] | FHA/VA government-guaranteed loans [Member]
Financing Receivable Recorded Investment [Line Items]
Financing Receivable, Originated in Current Fiscal Year	235
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	2,124
Financing Receivable, Originated Two Years before Latest Fiscal Year	2,900
Financing Receivable, Originated Three Years before Latest Fiscal Year	5,274
Financing Receivable, Originated Four Years before Latest Fiscal Year	10,406
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	141,863
Financing Receivable, Revolving	0
Loans held for investment	162,802	123,909
Residential Portfolio Segment [Member] | FHA/VA government-guaranteed loans [Member] | Puerto Rico and Virgin Islands regions [Member]
Financing Receivable Recorded Investment [Line Items]
Financing Receivable, Originated in Current Fiscal Year	235
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	2,124
Financing Receivable, Originated Two Years before Latest Fiscal Year	2,900
Financing Receivable, Originated Three Years before Latest Fiscal Year	4,987
Financing Receivable, Originated Four Years before Latest Fiscal Year	10,406
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	140,974
Financing Receivable, Revolving	0
Loans held for investment	161,626	122,429
Residential Portfolio Segment [Member] | FHA/VA government-guaranteed loans [Member] | Florida region [Member]
Financing Receivable Recorded Investment [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	287
Financing Receivable, Originated Four Years before Latest Fiscal Year	0
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	889
Financing Receivable, Revolving	0
Loans held for investment	1,176	1,480
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans held for investment	3,473,911	2,809,864
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | Puerto Rico and Virgin Islands regions [Member]
Financing Receivable Recorded Investment [Line Items]
Loans held for investment	2,938,733	2,245,158
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | Florida region [Member]
Financing Receivable Recorded Investment [Line Items]
Loans held for investment	535,178	564,706
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | Less than or equal to 90 percent [Member]
Financing Receivable Recorded Investment [Line Items]
Financing Receivable, Originated in Current Fiscal Year	49,248
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	118,033
Financing Receivable, Originated Two Years before Latest Fiscal Year	168,762
Financing Receivable, Originated Three Years before Latest Fiscal Year	163,167
Financing Receivable, Originated Four Years before Latest Fiscal Year	182,526
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	2,191,325
Financing Receivable, Revolving	0
Loans held for investment	2,873,061	2,234,190
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | Less than or equal to 90 percent [Member] | Puerto Rico and Virgin Islands regions [Member]
Financing Receivable Recorded Investment [Line Items]
Financing Receivable, Originated in Current Fiscal Year	26,931
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	64,816
Financing Receivable, Originated Two Years before Latest Fiscal Year	104,823
Financing Receivable, Originated Three Years before Latest Fiscal Year	70,490
Financing Receivable, Originated Four Years before Latest Fiscal Year	97,267
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	1,992,451
Financing Receivable, Revolving	0
Loans held for investment	2,356,778	1,684,340
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | Less than or equal to 90 percent [Member] | Florida region [Member]
Financing Receivable Recorded Investment [Line Items]
Financing Receivable, Originated in Current Fiscal Year	22,317
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	53,217
Financing Receivable, Originated Two Years before Latest Fiscal Year	63,939
Financing Receivable, Originated Three Years before Latest Fiscal Year	92,677
Financing Receivable, Originated Four Years before Latest Fiscal Year	85,259
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	198,874
Financing Receivable, Revolving	0
Loans held for investment	516,283	549,850
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | Greater than 90 percent but less than or equal to 100 percent [Member]
Financing Receivable Recorded Investment [Line Items]
Financing Receivable, Originated in Current Fiscal Year	9,622
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	9,148
Financing Receivable, Originated Two Years before Latest Fiscal Year	11,024
Financing Receivable, Originated Three Years before Latest Fiscal Year	8,372
Financing Receivable, Originated Four Years before Latest Fiscal Year	17,174
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	440,501
Financing Receivable, Revolving	0
Loans held for investment	495,841	475,675
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | Greater than 90 percent but less than or equal to 100 percent [Member] | Puerto Rico and Virgin Islands regions [Member]
Financing Receivable Recorded Investment [Line Items]
Financing Receivable, Originated in Current Fiscal Year	3,514
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	7,107
Financing Receivable, Originated Two Years before Latest Fiscal Year	8,068
Financing Receivable, Originated Three Years before Latest Fiscal Year	3,956
Financing Receivable, Originated Four Years before Latest Fiscal Year	14,838
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	439,463
Financing Receivable, Revolving	0
Loans held for investment	476,946	460,879
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | Greater than 90 percent but less than or equal to 100 percent [Member] | Florida region [Member]
Financing Receivable Recorded Investment [Line Items]
Financing Receivable, Originated in Current Fiscal Year	6,108
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	2,041
Financing Receivable, Originated Two Years before Latest Fiscal Year	2,956
Financing Receivable, Originated Three Years before Latest Fiscal Year	4,416
Financing Receivable, Originated Four Years before Latest Fiscal Year	2,336
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	1,038
Financing Receivable, Revolving	0
Loans held for investment	18,895	14,796
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | Greater than 100 percent [Member]
Financing Receivable Recorded Investment [Line Items]
Financing Receivable, Originated in Current Fiscal Year	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	943
Financing Receivable, Originated Two Years before Latest Fiscal Year	5,480
Financing Receivable, Originated Three Years before Latest Fiscal Year	3,116
Financing Receivable, Originated Four Years before Latest Fiscal Year	7,416
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	88,054
Financing Receivable, Revolving	0
Loans held for investment	105,009	99,999
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | Greater than 100 percent [Member] | Puerto Rico and Virgin Islands regions [Member]
Financing Receivable Recorded Investment [Line Items]
Financing Receivable, Originated in Current Fiscal Year	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	943
Financing Receivable, Originated Two Years before Latest Fiscal Year	5,480
Financing Receivable, Originated Three Years before Latest Fiscal Year	3,116
Financing Receivable, Originated Four Years before Latest Fiscal Year	7,416
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	88,054
Financing Receivable, Revolving	0
Loans held for investment	105,009	99,939
Residential Portfolio Segment [Member] | Conventional residential mortgage loans [Member] | Greater than 100 percent [Member] | Florida region [Member]
Financing Receivable Recorded Investment [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	0
Financing Receivable, Revolving	0
Loans held for investment	$ 0	$ 60