Amortized cost, gross unrealized gains and losses, approximate fair value, weighted average yield and contractual maturities of investment securities available-for-sale (Detail) - Entity [Domain] - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 5,568,667	$ 5,307,250
Gross Unrealized Gains	71,796	73,411
Gross Unrealized Losses	55,385	65,502
Investment securities available-for-sale, at fair value	$ 5,585,078	$ 5,315,159
Weighted Average Yield	2.11%	2.04%
US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 967,875	$ 698,003
Gross Unrealized Gains	5,906	2,226
Gross Unrealized Losses	58	75
Investment securities available-for-sale, at fair value	$ 973,723	$ 700,154
Weighted Average Yield	1.08%	1.14%
US Treasury Securities [Member] | Within One Year From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 25,279	$ 0
Gross Unrealized Gains	795	0
Gross Unrealized Losses	0	0
Investment securities available-for-sale, at fair value	$ 26,074	$ 0
Weighted Average Yield	3.99%	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	$ 942,596	$ 698,003
Gross Unrealized Gains	5,111	2,226
Gross Unrealized Losses	58	75
Investment securities available-for-sale, at fair value	$ 947,649	$ 700,154
Weighted Average Yield	1.00%	1.14%
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	$ 1,112,531	$ 1,735,758
Gross Unrealized Gains	2,532	1,606
Gross Unrealized Losses	4,691	12,391
Investment securities available-for-sale, at fair value	$ 1,110,372	$ 1,724,973
Weighted Average Yield	1.43%	1.31%
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	$ 35,180	$ 42,140
Gross Unrealized Gains	116	380
Gross Unrealized Losses	0	0
Investment securities available-for-sale, at fair value	$ 35,296	$ 42,520
Weighted Average Yield	1.85%	1.61%
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	$ 1,049,241	$ 1,603,245
Gross Unrealized Gains	2,390	1,168
Gross Unrealized Losses	4,450	9,936
Investment securities available-for-sale, at fair value	$ 1,047,181	$ 1,594,477
Weighted Average Yield	1.36%	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	$ 5,110	$ 67,373
Gross Unrealized Gains	26	58
Gross Unrealized Losses	17	2,271
Investment securities available-for-sale, at fair value	$ 5,119	$ 65,160
Weighted Average Yield	5.04%	1.72%
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	224	184
Investment securities available-for-sale, at fair value	$ 22,776	$ 22,816
Weighted Average Yield	3.20%	3.18%
Puerto Rico States And Political Subdivisions Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 60,970	$ 75,164
Gross Unrealized Gains	0	97
Gross Unrealized Losses	8,856	13,549
Investment securities available-for-sale, at fair value	$ 52,114	$ 61,712
Weighted Average Yield	5.94%	6.04%
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	$ 2,751	$ 2,765
Gross Unrealized Gains	0	17
Gross Unrealized Losses	11	0
Investment securities available-for-sale, at fair value	$ 2,740	$ 2,782
Weighted Average Yield	3.85%	3.83%
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	$ 7,099	$ 1,024
Gross Unrealized Gains	0	38
Gross Unrealized Losses	234	0
Investment securities available-for-sale, at fair value	$ 6,865	$ 1,062
Weighted Average Yield	4.05%	8.40%
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	$ 14,363	$ 22,552
Gross Unrealized Gains	0	2
Gross Unrealized Losses	2,123	2,331
Investment securities available-for-sale, at fair value	$ 12,240	$ 20,223
Weighted Average Yield	6.48%	5.82%
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	$ 36,757	$ 48,823
Gross Unrealized Gains	0	40
Gross Unrealized Losses	6,488	11,218
Investment securities available-for-sale, at fair value	$ 30,269	$ 37,645
Weighted Average Yield	6.24%	6.22%
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	$ 1,756,019	$ 1,934,652
Gross Unrealized Gains	13,329	14,181
Gross Unrealized Losses	32,519	38,803
Investment securities available-for-sale, at fair value	$ 1,736,829	$ 1,910,030
Weighted Average Yield	2.02%	2.04%
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	$ 18,353	$ 3,687
Gross Unrealized Gains	752	87
Gross Unrealized Losses	0	0
Investment securities available-for-sale, at fair value	$ 19,105	$ 3,774
Weighted Average Yield	2.98%	2.66%
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	$ 48,183	$ 25,202
Gross Unrealized Gains	1,172	985
Gross Unrealized Losses	0	0
Investment securities available-for-sale, at fair value	$ 49,355	$ 26,187
Weighted Average Yield	2.72%	2.93%
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	$ 1,689,483	$ 1,905,763
Gross Unrealized Gains	11,405	13,109
Gross Unrealized Losses	32,519	38,803
Investment securities available-for-sale, at fair value	$ 1,668,369	$ 1,880,069
Weighted Average Yield	1.99%	2.03%
Collateralized Mortgage Obligations Issued By Private Enterprise [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] | 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	$ 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 Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 1,659,342	$ 851,088
Gross Unrealized Gains	48,746	53,958
Gross Unrealized Losses	9,244	684
Investment securities available-for-sale, at fair value	$ 1,698,844	$ 904,362
Weighted Average Yield	3.11%	3.88%
Collateralized Mortgage Backed 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%
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	$ 22,848	$ 27,339
Gross Unrealized Gains	1,069	1,597
Gross Unrealized Losses	7	0
Investment securities available-for-sale, at fair value	$ 23,910	$ 28,936
Weighted Average Yield	3.58%	4.68%
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	$ 225,725	$ 147,182
Gross Unrealized Gains	6,723	7,314
Gross Unrealized Losses	280	1
Investment securities available-for-sale, at fair value	$ 232,168	$ 154,495
Weighted Average Yield	3.29%	3.51%
Collateralized Mortgage Backed Securities [Member] | More Than Ten Years From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 1,410,769	$ 676,567
Gross Unrealized Gains	40,954	45,047
Gross Unrealized Losses	8,957	683
Investment securities available-for-sale, at fair value	$ 1,442,766	$ 720,931
Weighted Average Yield	3.07%	3.93%
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 1,350	$ 1,351
Gross Unrealized Gains	1,247	1,271
Gross Unrealized Losses	3	0
Investment securities available-for-sale, at fair value	$ 2,594	$ 2,622
Weighted Average Yield	0.98%	5.03%
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 10,580	$ 11,234
Gross Unrealized Gains	36	72
Gross Unrealized Losses	14	0
Investment securities available-for-sale, at fair value	$ 10,602	$ 11,306
Weighted Average Yield	1.96%	2.03%
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	$ 9,095	$ 9,277
Gross Unrealized Gains	0	10
Gross Unrealized Losses	14	0
Investment securities available-for-sale, at fair value	$ 9,081	$ 9,287
Weighted Average Yield	1.69%	1.69%
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	$ 1,485	$ 1,957
Gross Unrealized Gains	36	62
Gross Unrealized Losses	0	0
Investment securities available-for-sale, at fair value	$ 1,521	$ 2,019
Weighted Average Yield	3.62%	3.63%
Other 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%