INVESTMENT SECURITIES - Available-For-Sale Investments' Fair Value And Gross Unrealized Losses (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule Of Available For Sale Securities [Line Items]
Fair Value Less than 12 months	$ 1,331,998	$ 778,485
Unrealized losses less than 12 months	19,090	6,803
Fair Value 12 months or more	43,302	366,045
Unrealized losses 12 months or more	24,034	37,097
Total Fair Value	1,375,300	1,144,530
Total unrealized losses	43,124	43,900
Debt Securities [Member] | 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	22,609	23,008
Unrealized losses 12 months or more	15,912	21,597
Total Fair Value	22,609	23,008
Total unrealized losses	15,912	21,597
Debt Securities [Member] | US States And Political Subdivisions [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value Less than 12 months	469,046	198,243
Unrealized losses less than 12 months	3,334	929
Fair Value 12 months or more	0	210,504
Unrealized losses 12 months or more	0	3,661
Total Fair Value	469,046	408,747
Total unrealized losses	3,334	4,590
Debt Securities [Member] | Equity Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value Less than 12 months	408
Unrealized losses less than 12 months	7
Fair Value 12 months or more	0
Unrealized losses 12 months or more	0
Total Fair Value	408
Total unrealized losses	7
Mortgage Backed Securities [Member] | Collateralized Mortgage Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value Less than 12 months	55,309
Unrealized losses less than 12 months	163
Fair Value 12 months or more	0
Unrealized losses 12 months or more	0
Total Fair Value	55,309
Total unrealized losses	163
Mortgage Backed Securities [Member] | Mortgage Backed Securities Issued By Private Enterprises [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	20,693	25,214
Unrealized losses 12 months or more	8,122	9,691
Total Fair Value	20,693	25,214
Total unrealized losses	8,122	9,691
Mortgage Backed Securities [Member] | Government National Mortgage Association Certificates And Obligations G N M A [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value Less than 12 months	43,388	1,047
Unrealized losses less than 12 months	92	20
Fair Value 12 months or more	0	0
Unrealized losses 12 months or more	0	0
Total Fair Value	43,388	1,047
Total unrealized losses	92	20
Mortgage Backed Securities [Member] | Federal National Mortgage Association Certificates And Obligations F N M A [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value Less than 12 months	519,008	437,305
Unrealized losses less than 12 months	9,667	4,516
Fair Value 12 months or more	0	88,013
Unrealized losses 12 months or more	0	1,780
Total Fair Value	519,008	525,318
Total unrealized losses	9,667	6,296
Mortgage Backed Securities [Member] | Federal Home Loan Mortgage Corporation Certificates And Obligations F H L M C [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value Less than 12 months	244,839	141,890
Unrealized losses less than 12 months	5,827	1,338
Fair Value 12 months or more	0	19,306
Unrealized losses 12 months or more	0	368
Total Fair Value	244,839	161,196
Total unrealized losses	$ 5,827	$ 1,706