INVESTMENT SECURITIES - Available-For-Sale Investments' Fair Value And Gross Unrealized Losses (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Schedule Of Available For Sale Securities [Line Items]
Fair Value Less than 12 months	$ 45,780	$ 778,485
Unrealized Losses Less than 12 months	48	6,803
Fair Value 12 months or more	47,725	366,045
Unrealized Losses 12 months or more	25,587	37,097
Total Fair Value	93,505	1,144,530
Total Unrealized Losses	25,635	43,900
Equity Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value Less than 12 months	1	0
Unrealized Losses Less than 12 months	0	0
Fair Value 12 months or more	0	0
Unrealized Losses 12 months or more	0	0
Total Fair Value	1	0
Total Unrealized Losses	0	0
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	21,243	23,008
Unrealized Losses 12 months or more	17,119	21,597
Total Fair Value	21,243	23,008
Total Unrealized Losses	17,119	21,597
Debt Securities [Member] | US States And Political Subdivisions Member [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value Less than 12 months	17,764	198,243
Unrealized Losses Less than 12 months	27	929
Fair Value 12 months or more	0	210,504
Unrealized Losses 12 months or more	0	3,661
Total Fair Value	17,764	408,747
Total Unrealized Losses	27	4,590
Mortgage Backed Securities [Member] | Collateralized Mortgage Obligations Member
Schedule Of Available For Sale Securities [Line Items]
Fair Value Less than 12 months		0
Unrealized Losses Less than 12 months		0
Fair Value 12 months or more		0
Unrealized Losses 12 months or more		0
Total Fair Value		0
Total Unrealized Losses		0
Mortgage Backed Securities [Member] | Other-mortgage pass-through trust certificates [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	24,505	25,214
Unrealized Losses 12 months or more	8,457	9,691
Total Fair Value	24,505	25,214
Total Unrealized Losses	8,457	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	0	1,047
Unrealized Losses Less than 12 months	0	20
Fair Value 12 months or more	1,055	0
Unrealized Losses 12 months or more	6	0
Total Fair Value	1,055	1,047
Total Unrealized Losses	6	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	28,015	437,305
Unrealized Losses Less than 12 months	21	4,516
Fair Value 12 months or more	0	88,013
Unrealized Losses 12 months or more	0	1,780
Total Fair Value	28,015	525,318
Total Unrealized Losses	21	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	0	141,890
Unrealized Losses Less than 12 months	0	1,338
Fair Value 12 months or more	922	19,306
Unrealized Losses 12 months or more	5	368
Total Fair Value	922	161,196
Total Unrealized Losses	$ 5	$ 1,706