INVESTMENT SECURITIES - Available-For-Sale Investments' Fair Value And Gross Unrealized Losses (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Schedule Of Available For Sale Securities [Line Items]
Fair Value Less than 12 months	$ 154,704	$ 1,232,981
Unrealized Losses Less than 12 months	703	59,230
Fair Value 12 months or more	1,085,415	143,119
Unrealized Losses 12 months or more	53,614	33,875
Total Fair Value	1,240,119	1,376,100
Total Unrealized Losses	54,317	93,105
Equity Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value Less than 12 months	14	33
Unrealized Losses Less than 12 months	21	2
Fair Value 12 months or more	0	0
Unrealized Losses 12 months or more	0	0
Total Fair Value	14	33
Total Unrealized Losses	21	2
Debt Securities [Member] | Puerto Rico Government Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value Less than 12 months	0	23,156
Unrealized Losses Less than 12 months	0	5,977
Fair Value 12 months or more	45,503	28,174
Unrealized Losses 12 months or more	14,759	13,701
Total Fair Value	45,503	51,330
Total Unrealized Losses	14,759	19,678
Debt Securities [Member] | US States And Political Subdivisions Member [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value Less than 12 months	34,617	175,369
Unrealized Losses Less than 12 months	132	8,913
Fair Value 12 months or more	255,600	74,126
Unrealized Losses 12 months or more	8,631	5,863
Total Fair Value	290,217	249,495
Total Unrealized Losses	8,763	14,776
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		81
Unrealized Losses 12 months or more		1
Total Fair Value		81
Total Unrealized Losses		1
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	36,000	40,738
Unrealized Losses 12 months or more	12,774	14,310
Total Fair Value	36,000	40,738
Total Unrealized Losses	12,774	14,310
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	71,267	748,215
Unrealized Losses Less than 12 months	326	33,626
Fair Value 12 months or more	558,555	0
Unrealized Losses 12 months or more	13,409	0
Total Fair Value	629,822	748,215
Total Unrealized Losses	13,735	33,626
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	48,806	286,208
Unrealized Losses Less than 12 months	224	10,712
Fair Value 12 months or more	189,757	0
Unrealized Losses 12 months or more	4,041	0
Total Fair Value	238,563	286,208
Total Unrealized Losses	$ 4,265	$ 10,712