INVESTMENT SECURITIES - Available-For-Sale Investments' Fair Value And Gross Unrealized Losses (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Schedule Of Available For Sale Securities [Line Items]
Fair Value Less than 12 months	$ 4,601,661	$ 782,960
Unrealized Losses Less than 12 months	76,269	1,610
Fair Value 12 months or more	1,008,607	44,465
Unrealized Losses 12 months or more	32,268	3,907
Total Fair Value	5,610,268	827,425
Total Unrealized Losses	108,537	5,517
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	2,850	2,899
Unrealized Losses 12 months or more	416	780
Total Fair Value	2,850	2,899
Total Unrealized Losses	416	780
U.S. Treasury and U.S. government agencies obligations
Schedule Of Available For Sale Securities [Line Items]
Fair Value Less than 12 months	1,717,340	425,155
Unrealized Losses Less than 12 months	25,401	621
Fair Value 12 months or more	606,179	23,377
Unrealized Losses 12 months or more	16,243	165
Total Fair Value	2,323,519	448,532
Total Unrealized Losses	41,644	786
MBS [Member] | FNMA [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value Less than 12 months	1,237,701	93,509
Unrealized Losses Less than 12 months	19,843	203
Fair Value 12 months or more	112,559	0
Unrealized Losses 12 months or more	3,821	0
Total Fair Value	1,350,260	93,509
Total Unrealized Losses	23,664	203
MBS [Member] | FHLMC [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value Less than 12 months	986,345	89,292
Unrealized Losses Less than 12 months	16,144	159
Fair Value 12 months or more	221,896	0
Unrealized Losses 12 months or more	8,481	0
Total Fair Value	1,208,241	89,292
Total Unrealized Losses	24,625	159
MBS [Member] | GNMA [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value Less than 12 months	194,271	70,504
Unrealized Losses Less than 12 months	1,329	217
Fair Value 12 months or more	41,233	0
Unrealized Losses 12 months or more	984	0
Total Fair Value	235,504	70,504
Total Unrealized Losses	2,313	217
MBS [Member] | Collateralized mortgage obligations guaranteed by FHLMC, FNMA and GNMA [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value Less than 12 months	466,004	104,500
Unrealized Losses Less than 12 months	13,552	410
Fair Value 12 months or more	16,656	9,761
Unrealized Losses 12 months or more	360	82
Total Fair Value	482,660	114,261
Total Unrealized Losses	13,912	492
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	7,234	8,428
Unrealized Losses 12 months or more	1,963	2,880
Total Fair Value	7,234	8,428
Total Unrealized Losses	$ 1,963	$ 2,880