INVESTMENT SECURITIES - Investment Securities Available for Sale (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Schedule of Available-for-sale Securities [Line Items]
Fair value	$ 1,932,178	$ 2,123,525
Weighted-average yield	2.50%	2.52%
Gross Unrealized loss	$ 6,562	$ 10,056
Gross Unrealized gain	63,431	24,573
Amortized cost	1,875,677	2,109,008
Allowance for Credit Losses	368	0
U S Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost Due within one year	7,483
Gross Unrealized gains Due within one year	99
Gross Unrealized losses Due within one year	0
Allowance for Credit Losses Within one year	0
Fair value Due within one year	$ 7,582
Weighted-average yield Due within one year	1.65%
Amortized cost After 1 to 5 years		7,478
Gross Unrealized gains After 1 to 5 years		1
Gross Unrealized losses After 1 to 5 years		0
Fair value After 1 to 5 years		$ 7,479
Weighted-average yield After 1 to 5 years		1.65%
U.S. government-sponsored agencies obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost Due within one year	$ 90,002	$ 93,299
Gross Unrealized gains Due within one year	510	103
Gross Unrealized losses Due within one year	0	106
Allowance for Credit Losses Within one year	0
Fair value Due within one year	$ 90,512	$ 93,296
Weighted-average yield Due within one year	1.56%	1.67%
Amortized cost After 1 to 5 years	$ 118,454	$ 142,513
Gross Unrealized gains After 1 to 5 years	1,488	676
Gross Unrealized losses After 1 to 5 years	0	52
Allowance for Credit Losses After 1 to 5 years	0
Fair value After 1 to 5 years	$ 119,942	$ 143,137
Weighted-average yield After 1 to 5 years	2.04%	2.12%
Amortized cost After 5 to 10 years	$ 112,477	$ 63,764
Gross Unrealized gains After 5 to 10 years	978	165
Gross Unrealized losses After 5 to 10 years	12	150
Fair value After 5 to 10 years	$ 113,443	$ 63,779
Weighted-average yield After 5 to 10 years	2.06%	2.33%
Amortized cost After 10 years	$ 23,306	$ 24,624
Gross Unrealized gains After 10 years	2	0
Gross Unrealized losses After 10 years	64	116
Allowance for Credit Losses After 10 years	0
Fair value After 10 years	$ 23,244	$ 24,508
Weighted-average yield After 10 years	0.65%	2.00%
Allowance for Credit Losses After 5 to 10 years	$ 0
Puerto Rico Government obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost After 5 to 10 years	4,000	$ 4,000
Gross Unrealized gains After 5 to 10 years	361	348
Gross Unrealized losses After 5 to 10 years	0	0
Fair value After 5 to 10 years	$ 4,361	$ 4,348
Weighted-average yield After 5 to 10 years	5.12%	5.12%
Amortized cost After 10 years	$ 4,113	$ 4,166
Gross Unrealized gains After 10 years	0	0
Gross Unrealized losses After 10 years	1,144	1,192
Allowance for Credit Losses After 10 years	0
Fair value After 10 years	$ 2,969	$ 2,974
Weighted-average yield After 10 years	6.97%	6.97%
Fair value	$ 7,300
Allowance for Credit Losses After 5 to 10 years	0
United States And Puerto Rico Government Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value	$ 362,053	$ 339,521
Weighted-average yield	1.92%	2.11%
Gross Unrealized loss	$ 1,220	$ 1,616
Gross Unrealized gain	3,438	1,293
Amortized cost	359,835	339,844
Allowance for Credit Losses	0
Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value	$ 1,569,625	$ 1,783,504
Weighted-average yield	2.63%	2.60%
Gross Unrealized loss	$ 5,342	$ 8,440
Gross Unrealized gain	59,993	23,280
Amortized cost	1,515,342	1,768,664
Allowance for Credit Losses	368
Mortgage Backed Securities [Member] | FHLMC [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost Due within one year	100
Gross Unrealized gains Due within one year	8
Gross Unrealized losses Due within one year	0
Allowance for Credit Losses Within one year	0
Fair value Due within one year	$ 108
Weighted-average yield Due within one year	4.87%
Amortized cost After 5 to 10 years	$ 76,460	81,418
Gross Unrealized gains After 5 to 10 years	2,426	589
Gross Unrealized losses After 5 to 10 years	0	228
Fair value After 5 to 10 years	$ 78,886	$ 81,779
Weighted-average yield After 5 to 10 years	2.15%	2.16%
Amortized cost After 10 years	$ 295,944	$ 424,316
Gross Unrealized gains After 10 years	10,832	3,873
Gross Unrealized losses After 10 years	2	758
Allowance for Credit Losses After 10 years	0
Fair value After 10 years	$ 306,774	$ 427,431
Weighted-average yield After 10 years	2.49%	2.50%
Fair value	$ 385,768	$ 509,210
Weighted-average yield	2.42%	2.44%
Gross Unrealized loss	$ 2	$ 986
Gross Unrealized gain	13,266	4,462
Amortized cost	372,504	505,734
Allowance for Credit Losses After 5 to 10 years	0
Allowance for Credit Losses	0
Mortgage Backed Securities [Member] | GNMA [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost After 1 to 5 years	5,808	4,357
Gross Unrealized gains After 1 to 5 years	141	45
Gross Unrealized losses After 1 to 5 years	0	0
Allowance for Credit Losses After 1 to 5 years	0
Fair value After 1 to 5 years	$ 5,949	$ 4,402
Weighted-average yield After 1 to 5 years	3.23%	3.26%
Amortized cost After 5 to 10 years	$ 37,206	$ 42,303
Gross Unrealized gains After 5 to 10 years	970	607
Gross Unrealized losses After 5 to 10 years	0	0
Fair value After 5 to 10 years	$ 38,176	$ 42,910
Weighted-average yield After 5 to 10 years	2.74%	2.77%
Amortized cost After 10 years	$ 303,796	$ 258,944
Gross Unrealized gains After 10 years	15,120	7,126
Gross Unrealized losses After 10 years	2	500
Allowance for Credit Losses After 10 years	0
Fair value After 10 years	$ 318,914	$ 265,570
Weighted-average yield After 10 years	3.12%	3.03%
Fair value	$ 363,039	$ 312,882
Weighted-average yield	3.08%	3.00%
Gross Unrealized loss	$ 2	$ 500
Gross Unrealized gain	16,231	7,778
Amortized cost	346,810	305,604
Allowance for Credit Losses After 5 to 10 years	0
Allowance for Credit Losses	0
Mortgage Backed Securities [Member] | FNMA [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost After 1 to 5 years	19,773	19,779
Gross Unrealized gains After 1 to 5 years	750	415
Gross Unrealized losses After 1 to 5 years	0	3
Allowance for Credit Losses After 1 to 5 years	0
Fair value After 1 to 5 years	$ 20,523	$ 20,191
Weighted-average yield After 1 to 5 years	2.79%	2.79%
Amortized cost After 5 to 10 years	$ 133,479	$ 140,599
Gross Unrealized gains After 5 to 10 years	5,218	1,257
Gross Unrealized losses After 5 to 10 years	0	641
Fair value After 5 to 10 years	$ 138,697	$ 141,215
Weighted-average yield After 5 to 10 years	2.14%	2.14%
Amortized cost After 10 years	$ 540,107	$ 700,213
Gross Unrealized gains After 10 years	23,238	9,006
Gross Unrealized losses After 10 years	0	1,208
Allowance for Credit Losses After 10 years	0
Fair value After 10 years	$ 563,345	$ 708,011
Weighted-average yield After 10 years	2.61%	2.58%
Fair value	$ 722,565	$ 869,417
Weighted-average yield	2.52%	2.51%
Gross Unrealized loss	$ 0	$ 1,852
Gross Unrealized gain	29,206	10,678
Amortized cost	693,359	860,591
Allowance for Credit Losses After 5 to 10 years	0
Allowance for Credit Losses	0
Mortgage Backed Securities [Member] | Collateralized mortgage obligations guaranteed by the FHLMC, FNMA and GNMA [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost After 1 to 5 years	606	608
Gross Unrealized gains After 1 to 5 years	0	0
Gross Unrealized losses After 1 to 5 years	3	1
Allowance for Credit Losses After 1 to 5 years	0
Fair value After 1 to 5 years	$ 603	$ 607
Weighted-average yield After 1 to 5 years	1.66%	2.43%
Amortized cost After 10 years	$ 86,706	$ 80,130
Gross Unrealized gains After 10 years	1,290	362
Gross Unrealized losses After 10 years	646	220
Allowance for Credit Losses After 10 years	0
Fair value After 10 years	$ 87,350	$ 80,272
Weighted-average yield After 10 years	2.50%	2.76%
Fair value	$ 87,953	$ 80,879
Weighted-average yield	2.49%	2.75%
Gross Unrealized loss	$ 649	$ 221
Gross Unrealized gain	1,290	362
Amortized cost	87,312	80,738
Allowance for Credit Losses	0
Mortgage Backed Securities [Member] | Private label [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost After 10 years	15,357	15,997
Gross Unrealized gains After 10 years	0	0
Gross Unrealized losses After 10 years	4,689	4,881
Allowance for Credit Losses After 10 years	368
Fair value After 10 years	$ 10,300	$ 11,116
Weighted-average yield After 10 years	3.45%	3.90%
Fair value	$ 10,300
Weighted-average yield	3.45%
Gross Unrealized loss	$ 4,700
Allowance for Credit Losses	368	$ 0
Other Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost After 1 to 5 years	500	500
Gross Unrealized gains After 1 to 5 years	0	0
Gross Unrealized losses After 1 to 5 years	0	0
Allowance for Credit Losses After 1 to 5 years	0
Fair value After 1 to 5 years	$ 500	$ 500
Weighted-average yield After 1 to 5 years	2.95%	2.95%