Amortized cost, gross unrealized gains and losses, approximate fair value, weighted average yield and contractual maturities of investment securities available-for-sale (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 5,745,437	$ 5,345,877
Gross Unrealized Gains	75,519	79,357
Gross Unrealized Losses	93,190	130,434
Investment securities available-for-sale, at fair value	5,727,766	5,294,800
Weighted Average Yield	2.04%	2.30%
US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	591,928	26,474
Gross Unrealized Gains	1,567	2,008
Gross Unrealized Losses	685	0
Investment securities available-for-sale, at fair value	592,810	28,482
Weighted Average Yield	1.15%	3.85%
US Treasury Securities [Member] | Within One Year From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	0	0
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Investment securities available-for-sale, at fair value	0	0
Weighted Average Yield	0.00%	0.00%
US Treasury Securities [Member] | More Than One And Within Five Years From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	591,928	26,474
Gross Unrealized Gains	1,567	2,008
Gross Unrealized Losses	685	0
Investment securities available-for-sale, at fair value	592,810	28,482
Weighted Average Yield	1.15%	3.85%
US Treasury Securities [Member] | More Than Five And Within Ten Years From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	0	0
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Investment securities available-for-sale, at fair value	0	0
Weighted Average Yield	0.00%	0.00%
US Treasury Securities [Member] | More Than Ten Years From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	0	0
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Investment securities available-for-sale, at fair value	0	0
Weighted Average Yield	0.00%	0.00%
US Government Sponsored Enterprises Debt Securities Member
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,991,695	1,664,085
Gross Unrealized Gains	1,622	1,817
Gross Unrealized Losses	19,912	36,697
Investment securities available-for-sale, at fair value	1,973,405	1,629,205
Weighted Average Yield	1.27%	1.38%
US Government Sponsored Enterprises Debt Securities Member | Within One Year From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	32,119	25,021
Gross Unrealized Gains	417	39
Gross Unrealized Losses	0	0
Investment securities available-for-sale, at fair value	32,536	25,060
Weighted Average Yield	1.61%	1.85%
US Government Sponsored Enterprises Debt Securities Member | More Than One And Within Five Years From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,785,955	1,087,453
Gross Unrealized Gains	1,125	1,678
Gross Unrealized Losses	12,997	12,715
Investment securities available-for-sale, at fair value	1,774,083	1,076,416
Weighted Average Yield	1.22%	1.26%
US Government Sponsored Enterprises Debt Securities Member | More Than Five And Within Ten Years From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	150,621	528,611
Gross Unrealized Gains	80	100
Gross Unrealized Losses	6,124	21,742
Investment securities available-for-sale, at fair value	144,577	506,969
Weighted Average Yield	1.53%	1.52%
US Government Sponsored Enterprises Debt Securities Member | More Than Ten Years From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	23,000	23,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	791	2,240
Investment securities available-for-sale, at fair value	22,209	20,760
Weighted Average Yield	3.16%	3.12%
Puerto Rico States And Political Subdivisions Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	76,827	78,178
Gross Unrealized Gains	103	74
Gross Unrealized Losses	10,812	11,875
Investment securities available-for-sale, at fair value	66,118	66,377
Weighted Average Yield	6.03%	5.89%
Puerto Rico States And Political Subdivisions Debt Securities [Member] | Within One Year From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,755	0
Gross Unrealized Gains	6	0
Gross Unrealized Losses	0	0
Investment securities available-for-sale, at fair value	1,761	0
Weighted Average Yield	5.41%	0.00%
Puerto Rico States And Political Subdivisions Debt Securities [Member] | More Than One And Within Five Years From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,790	6,228
Gross Unrealized Gains	41	45
Gross Unrealized Losses	16	85
Investment securities available-for-sale, at fair value	3,815	6,188
Weighted Average Yield	4.96%	4.64%
Puerto Rico States And Political Subdivisions Debt Securities [Member] | More Than Five And Within Ten Years From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	22,452	23,147
Gross Unrealized Gains	1	0
Gross Unrealized Losses	1,728	1,978
Investment securities available-for-sale, at fair value	20,725	21,169
Weighted Average Yield	5.83%	6.33%
Puerto Rico States And Political Subdivisions Debt Securities [Member] | More Than Ten Years From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	48,830	48,803
Gross Unrealized Gains	55	29
Gross Unrealized Losses	9,068	9,812
Investment securities available-for-sale, at fair value	39,817	39,020
Weighted Average Yield	6.23%	5.84%
Collateralized Mortgage Obligations Issued By U S Government Sponsored Enterprises And U S Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,179,080	2,474,765
Gross Unrealized Gains	15,332	19,554
Gross Unrealized Losses	59,338	76,023
Investment securities available-for-sale, at fair value	2,135,074	2,418,296
Weighted Average Yield	2.07%	2.06%
Collateralized Mortgage Obligations Issued By U S Government Sponsored Enterprises And U S Government [Member] | Within One Year From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	0	0
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Investment securities available-for-sale, at fair value	0	0
Weighted Average Yield	0.00%	0.00%
Collateralized Mortgage Obligations Issued By U S Government Sponsored Enterprises And U S Government [Member] | More Than One And Within Five Years From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,235	5,131
Gross Unrealized Gains	114	101
Gross Unrealized Losses	0	0
Investment securities available-for-sale, at fair value	4,349	5,232
Weighted Average Yield	2.62%	1.79%
Collateralized Mortgage Obligations Issued By U S Government Sponsored Enterprises And U S Government [Member] | More Than Five And Within Ten Years From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	26,540	31,613
Gross Unrealized Gains	1,020	921
Gross Unrealized Losses	7	0
Investment securities available-for-sale, at fair value	27,553	32,534
Weighted Average Yield	2.90%	2.98%
Collateralized Mortgage Obligations Issued By U S Government Sponsored Enterprises And U S Government [Member] | More Than Ten Years From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,148,305	2,438,021
Gross Unrealized Gains	14,198	18,532
Gross Unrealized Losses	59,331	76,023
Investment securities available-for-sale, at fair value	2,103,172	2,380,530
Weighted Average Yield	2.06%	2.05%
Collateralized Mortgage Obligations Issued By Private Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	6	509
Gross Unrealized Gains	0	4
Gross Unrealized Losses	0	0
Investment securities available-for-sale, at fair value	6	513
Weighted Average Yield	0.05%	3.78%
Collateralized Mortgage Obligations Issued By Private Enterprise [Member] | Within One Year From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	0	0
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Investment securities available-for-sale, at fair value	0	0
Weighted Average Yield	0.00%	0.00%
Collateralized Mortgage Obligations Issued By Private Enterprise [Member] | More Than One And Within Five Years From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	0	0
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Investment securities available-for-sale, at fair value	0	0
Weighted Average Yield	0.00%	0.00%
Collateralized Mortgage Obligations Issued By Private Enterprise [Member] | More Than Five And Within Ten Years From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	0	0
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Investment securities available-for-sale, at fair value	0	0
Weighted Average Yield	0.00%	0.00%
Collateralized Mortgage Obligations Issued By Private Enterprise [Member] | More Than Ten Years From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	6	509
Gross Unrealized Gains	0	4
Gross Unrealized Losses	0	0
Investment securities available-for-sale, at fair value	6	513
Weighted Average Yield	0.05%	3.78%
Collateralized Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	891,204	1,086,446
Gross Unrealized Gains	55,600	54,722
Gross Unrealized Losses	2,235	5,527
Investment securities available-for-sale, at fair value	944,569	1,135,641
Weighted Average Yield	3.95%	3.95%
Collateralized Mortgage Backed Securities [Member] | Within One Year From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	0	419
Gross Unrealized Gains	0	24
Gross Unrealized Losses	0	0
Investment securities available-for-sale, at fair value	0	443
Weighted Average Yield	0.00%	3.14%
Collateralized Mortgage Backed Securities [Member] | More Than One And Within Five Years From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	30,049	15,921
Gross Unrealized Gains	1,674	833
Gross Unrealized Losses	0	0
Investment securities available-for-sale, at fair value	31,723	16,754
Weighted Average Yield	4.69%	4.50%
Collateralized Mortgage Backed Securities [Member] | More Than Five And Within Ten Years From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	180,944	62,373
Gross Unrealized Gains	8,262	3,058
Gross Unrealized Losses	377	1,214
Investment securities available-for-sale, at fair value	188,829	64,217
Weighted Average Yield	3.41%	4.12%
Collateralized Mortgage Backed Securities [Member] | More Than Ten Years From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	680,211	1,007,733
Gross Unrealized Gains	45,664	50,807
Gross Unrealized Losses	1,858	4,313
Investment securities available-for-sale, at fair value	724,017	1,054,227
Weighted Average Yield	4.06%	3.93%
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,178	3,178
Gross Unrealized Gains	1,220	1,109
Gross Unrealized Losses	157	171
Investment securities available-for-sale, at fair value	4,241	4,116
Weighted Average Yield	6.01%	4.06%
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	11,519	12,242
Gross Unrealized Gains	75	69
Gross Unrealized Losses	51	141
Investment securities available-for-sale, at fair value	11,543	12,170
Weighted Average Yield	2.05%	2.09%
Other Securities [Member] | Within One Year From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	0	0
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Investment securities available-for-sale, at fair value	0	0
Weighted Average Yield	0.00%	0.00%
Other Securities [Member] | More Than One And Within Five Years From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	9,368	9,638
Gross Unrealized Gains	0	0
Gross Unrealized Losses	51	141
Investment securities available-for-sale, at fair value	9,317	9,497
Weighted Average Yield	1.69%	1.68%
Other Securities [Member] | More Than Five And Within Ten Years From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,151	0
Gross Unrealized Gains	75	0
Gross Unrealized Losses	0	0
Investment securities available-for-sale, at fair value	2,226	0
Weighted Average Yield	3.63%	0.00%
Other Securities [Member] | More Than Ten Years From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	0	2,604
Gross Unrealized Gains	0	69
Gross Unrealized Losses	0	0
Investment securities available-for-sale, at fair value	$ 0	$ 2,673
Weighted Average Yield	0.00%	3.61%