DEBT SECURITIES - Available-For-Sale Investments' Fair Value And Gross Unrealized Losses (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Schedule Of Available For Sale Securities [Line Items]
Fair Value Less than 12 months	$ 26,180	$ 1,115,192
Unrealized Losses Less than 12 months	120	125,343
Fair Value 12 months or more	5,170,265	4,447,686
Unrealized Losses 12 months or more	632,929	673,123
Total Fair Value	5,196,445	5,562,878
Total Unrealized Losses	633,049	798,466
Allowance for Credit Losses	511	458
U.S. Treasury and U.S. government agencies obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value Less than 12 months	2,544	298,313
Unrealized Losses Less than 12 months	2	18,057
Fair Value 12 months or more	2,428,784	2,174,724
Unrealized Losses 12 months or more	157,026	231,357
Total Fair Value	2,431,328	2,473,037
Total Unrealized Losses	157,028	249,414
Puerto Rico government obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value Less than 12 months	0	0
Unrealized Losses Less than 12 months	0	0
Fair Value 12 months or more	1,415	2,201
Unrealized Losses 12 months or more	1,346	755
Total Fair Value	1,415	2,201
Total Unrealized Losses	1,346	755
Allowance for Credit Losses	400	400
Residential MBS [Member]
Schedule Of Available For Sale Securities [Line Items]
Allowance for Credit Losses	116	83
Residential MBS [Member] | Private label [Member]
Schedule Of Available For Sale Securities [Line Items]
Allowance for Credit Losses	100	100
Residential MBS [Member] | FHLMC [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value Less than 12 months	9	260,524
Unrealized Losses Less than 12 months	0	45,424
Fair Value 12 months or more	988,092	831,637
Unrealized Losses 12 months or more	174,786	160,012
Total Fair Value	988,101	1,092,161
Total Unrealized Losses	174,786	205,436
Residential MBS [Member] | GNMA [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value Less than 12 months	12,257	74,829
Unrealized Losses Less than 12 months	100	3,433
Fair Value 12 months or more	202,390	179,854
Unrealized Losses 12 months or more	25,808	28,167
Total Fair Value	214,647	254,683
Total Unrealized Losses	25,908	31,600
Residential MBS [Member] | FNMA [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value Less than 12 months	0	405,977
Unrealized Losses Less than 12 months	0	49,479
Fair Value 12 months or more	1,183,275	920,200
Unrealized Losses 12 months or more	180,913	169,419
Total Fair Value	1,183,275	1,326,177
Total Unrealized Losses	180,913	218,898
Residential MBS [Member] | CMOs issued or guaranteed by the FHLMC, FNMA, and GNMA: [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value Less than 12 months	0	45,370
Unrealized Losses Less than 12 months	0	6,735
Fair Value 12 months or more	221,276	200,323
Unrealized Losses 12 months or more	52,263	49,804
Total Fair Value	221,276	245,693
Total Unrealized Losses	52,263	56,539
Residential MBS [Member] | Private label [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value Less than 12 months	0	0
Unrealized Losses Less than 12 months	0	0
Fair Value 12 months or more	4,785	5,794
Unrealized Losses 12 months or more	2,185	2,026
Total Fair Value	4,785	5,794
Total Unrealized Losses	2,185	2,026
Commercial MBS [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value Less than 12 months	11,370	30,179
Unrealized Losses Less than 12 months	18	2,215
Fair Value 12 months or more	140,248	132,953
Unrealized Losses 12 months or more	38,602	31,583
Total Fair Value	151,618	163,132
Total Unrealized Losses	38,620	33,798
Allowance for Credit Losses	$ 0	$ 0