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	Jun. 30, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 5,087,765	$ 4,911,736
Gross Unrealized Gains	98,591	173,990
Gross Unrealized Losses	71,720	1,525
Fair Value	5,114,636	5,084,201
Weighted Average Yield	2.44%	2.94%
US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	41,858	34,254
Gross Unrealized Gains	2,375	2,984
Gross Unrealized Losses	0	0
Fair Value	44,233	37,238
Weighted Average Yield	2.49%	3.39%
US Treasury Securities [Member] | Within One Year From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	14,996	7,018
Gross Unrealized Gains	1	20
Gross Unrealized Losses	0	0
Fair Value	14,997	7,038
Weighted Average Yield	0.07%	1.67%
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	26,862	27,236
Gross Unrealized Gains	2,374	2,964
Gross Unrealized Losses	0	0
Fair Value	29,236	30,200
Weighted Average Yield	3.84%	3.83%
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
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
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	1,162,412	1,083,976
Gross Unrealized Gains	2,522	12,934
Gross Unrealized Losses	29,816	592
Fair Value	1,135,118	1,096,318
Weighted Average Yield	1.56%	2.60%
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	43,256	460,319
Gross Unrealized Gains	317	7,614
Gross Unrealized Losses	0	0
Fair Value	43,573	467,933
Weighted Average Yield	1.46%	3.82%
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	234,827	167,177
Gross Unrealized Gains	1,063	2,057
Gross Unrealized Losses	3,099	0
Fair Value	232,791	169,234
Weighted Average Yield	1.37%	1.59%
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	861,329	456,480
Gross Unrealized Gains	1,142	3,263
Gross Unrealized Losses	25,363	592
Fair Value	837,108	459,151
Weighted Average Yield	1.57%	1.74%
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	0
Gross Unrealized Gains	0	0
Gross Unrealized Losses	1,354	0
Fair Value	21,646	0
Weighted Average Yield	3.09%	0.00%
Puerto Rico States And Political Subdivisions Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	49,195	54,252
Gross Unrealized Gains	60	804
Gross Unrealized Losses	1,997	75
Fair Value	47,258	54,981
Weighted Average Yield	5.10%	4.91%
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	115	5,220
Gross Unrealized Gains	1	26
Gross Unrealized Losses	0	0
Fair Value	116	5,246
Weighted Average Yield	5.22%	3.08%
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	6,241	6,254
Gross Unrealized Gains	57	130
Gross Unrealized Losses	32	39
Fair Value	6,266	6,345
Weighted Average Yield	4.66%	4.65%
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	5,619	5,513
Gross Unrealized Gains	0	0
Gross Unrealized Losses	165	36
Fair Value	5,454	5,477
Weighted Average Yield	3.70%	3.79%
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	37,220	37,265
Gross Unrealized Gains	2	648
Gross Unrealized Losses	1,800	0
Fair Value	35,422	37,913
Weighted Average Yield	5.38%	5.38%
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	2,663,926	2,315,008
Gross Unrealized Gains	28,001	52,569
Gross Unrealized Losses	35,720	512
Fair Value	2,656,207	2,367,065
Weighted Average Yield	2.05%	2.22%
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
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	5,747	4,927
Gross Unrealized Gains	131	35
Gross Unrealized Losses	0	0
Fair Value	5,878	4,962
Weighted Average Yield	1.98%	1.48%
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	26,578	39,897
Gross Unrealized Gains	850	1,794
Gross Unrealized Losses	0	0
Fair Value	27,428	41,691
Weighted Average Yield	2.86%	2.94%
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	2,631,601	2,270,184
Gross Unrealized Gains	27,020	50,740
Gross Unrealized Losses	35,720	512
Fair Value	2,622,901	2,320,412
Weighted Average Yield	2.04%	2.21%
Collateralized Mortgage Obligations Issued By Private Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,187	2,414
Gross Unrealized Gains	18	59
Gross Unrealized Losses	0	0
Fair Value	1,205	2,473
Weighted Average Yield	4.12%	4.59%
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
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
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
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	1,187	2,414
Gross Unrealized Gains	18	59
Gross Unrealized Losses	0	0
Fair Value	1,205	2,473
Weighted Average Yield	4.12%	4.59%
Collateralized Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,149,776	1,383,356
Gross Unrealized Gains	63,359	99,920
Gross Unrealized Losses	3,718	129
Fair Value	1,209,417	1,483,147
Weighted Average Yield	4.12%	4.21%
Collateralized Mortgage Backed Securities [Member] | Within One Year From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	15	288
Gross Unrealized Gains	1	13
Gross Unrealized Losses	0	0
Fair Value	16	301
Weighted Average Yield	1.75%	3.47%
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	7,253	3,838
Gross Unrealized Gains	386	191
Gross Unrealized Losses	0	0
Fair Value	7,639	4,029
Weighted Average Yield	4.63%	4.12%
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	84,122	81,645
Gross Unrealized Gains	4,314	6,207
Gross Unrealized Losses	950	0
Fair Value	87,486	87,852
Weighted Average Yield	4.25%	4.71%
Collateralized Mortgage Backed Securities [Member] | More Than Ten Years From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,058,386	1,297,585
Gross Unrealized Gains	58,658	93,509
Gross Unrealized Losses	2,768	129
Fair Value	1,114,276	1,390,965
Weighted Average Yield	4.11%	4.18%
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	6,506	6,507
Gross Unrealized Gains	2,189	909
Gross Unrealized Losses	53	10
Fair Value	8,642	7,406
Weighted Average Yield	3.17%	3.46%
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	12,905	31,969
Gross Unrealized Gains	67	3,811
Gross Unrealized Losses	416	207
Fair Value	12,556	35,573
Weighted Average Yield	2.14%	7.17%
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
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	9,816	9,992
Gross Unrealized Gains	0	0
Gross Unrealized Losses	416	207
Fair Value	9,400	9,785
Weighted Average Yield	1.68%	1.67%
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	0	18,032
Gross Unrealized Gains	0	3,675
Gross Unrealized Losses	0	0
Fair Value	0	21,707
Weighted Average Yield	0.00%	11.00%
Other Securities [Member] | More Than Ten Years From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,089	3,945
Gross Unrealized Gains	67	136
Gross Unrealized Losses	0	0
Fair Value	$ 3,156	$ 4,081
Weighted Average Yield	3.63%	3.62%