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	Sep. 30, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 5,141,845	$ 4,911,736
Gross Unrealized Gains	93,987	173,990
Gross Unrealized Losses	99,214	1,525
Fair Value	5,136,618	5,084,201
Weighted Average Yield	2.40%	2.94%
US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	41,669	34,254
Gross Unrealized Gains	2,259	2,984
Gross Unrealized Losses	0	0
Fair Value	43,928	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	15,000	7,018
Gross Unrealized Gains	0	20
Gross Unrealized Losses	0	0
Fair Value	15,000	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	26,669	27,236
Gross Unrealized Gains	2,259	2,964
Gross Unrealized Losses	0	0
Fair Value	28,928	30,200
Weighted Average Yield	3.85%	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	1,309,161	1,083,976
Gross Unrealized Gains	2,290	12,934
Gross Unrealized Losses	26,052	592
Fair Value	1,285,399	1,096,318
Weighted Average Yield	1.50%	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	43,130	460,319
Gross Unrealized Gains	182	7,614
Gross Unrealized Losses	0	0
Fair Value	43,312	467,933
Weighted Average Yield	1.47%	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	506,739	167,177
Gross Unrealized Gains	1,951	2,057
Gross Unrealized Losses	4,661	0
Fair Value	504,029	169,234
Weighted Average Yield	1.38%	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	736,292	456,480
Gross Unrealized Gains	157	3,263
Gross Unrealized Losses	19,785	592
Fair Value	716,664	459,151
Weighted Average Yield	1.53%	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	1,606	0
Fair Value	21,394	0
Weighted Average Yield	3.11%	0.00%
Puerto Rico States And Political Subdivisions Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	68,639	54,252
Gross Unrealized Gains	45	804
Gross Unrealized Losses	12,757	75
Fair Value	55,927	54,981
Weighted Average Yield	5.69%	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	0	5,220
Gross Unrealized Gains	0	26
Gross Unrealized Losses	0	0
Fair Value	0	5,246
Weighted Average Yield	0.00%	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	6,234	6,254
Gross Unrealized Gains	45	130
Gross Unrealized Losses	99	39
Fair Value	6,180	6,345
Weighted Average Yield	4.67%	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	7,820	5,513
Gross Unrealized Gains	0	0
Gross Unrealized Losses	107	36
Fair Value	7,713	5,477
Weighted Average Yield	4.88%	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	54,585	37,265
Gross Unrealized Gains	0	648
Gross Unrealized Losses	12,551	0
Fair Value	42,034	37,913
Weighted Average Yield	5.92%	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	2,563,951	2,315,008
Gross Unrealized Gains	25,788	52,569
Gross Unrealized Losses	55,995	512
Fair Value	2,533,744	2,367,065
Weighted Average Yield	2.06%	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	5,865	4,927
Gross Unrealized Gains	101	35
Gross Unrealized Losses	0	0
Fair Value	5,966	4,962
Weighted Average Yield	1.74%	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	22,433	39,897
Gross Unrealized Gains	638	1,794
Gross Unrealized Losses	0	0
Fair Value	23,071	41,691
Weighted Average Yield	2.93%	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	2,535,653	2,270,184
Gross Unrealized Gains	25,049	50,740
Gross Unrealized Losses	55,995	512
Fair Value	2,504,707	2,320,412
Weighted Average Yield	2.05%	2.21%
Collateralized Mortgage Obligations Issued By Private Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	877	2,414
Gross Unrealized Gains	10	59
Gross Unrealized Losses	0	0
Fair Value	887	2,473
Weighted Average Yield	3.76%	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	877	2,414
Gross Unrealized Gains	10	59
Gross Unrealized Losses	0	0
Fair Value	887	2,473
Weighted Average Yield	3.76%	4.59%
Collateralized Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,138,513	1,383,356
Gross Unrealized Gains	61,052	99,920
Gross Unrealized Losses	3,961	129
Fair Value	1,195,604	1,483,147
Weighted Average Yield	3.98%	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	756	288
Gross Unrealized Gains	45	13
Gross Unrealized Losses	0	0
Fair Value	801	301
Weighted Average Yield	3.40%	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	7,235	3,838
Gross Unrealized Gains	348	191
Gross Unrealized Losses	0	0
Fair Value	7,583	4,029
Weighted Average Yield	4.85%	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	76,962	81,645
Gross Unrealized Gains	3,786	6,207
Gross Unrealized Losses	1,106	0
Fair Value	79,642	87,852
Weighted Average Yield	4.21%	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	1,053,560	1,297,585
Gross Unrealized Gains	56,873	93,509
Gross Unrealized Losses	2,855	129
Fair Value	1,107,578	1,390,965
Weighted Average Yield	3.96%	4.18%
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	6,506	6,507
Gross Unrealized Gains	2,466	909
Gross Unrealized Losses	186	10
Fair Value	8,786	7,406
Weighted Average Yield	3.35%	3.46%
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	12,529	31,969
Gross Unrealized Gains	77	3,811
Gross Unrealized Losses	263	207
Fair Value	12,343	35,573
Weighted Average Yield	2.11%	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	9,727	9,992
Gross Unrealized Gains	0	0
Gross Unrealized Losses	263	207
Fair Value	9,464	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	2,802	3,945
Gross Unrealized Gains	77	136
Gross Unrealized Losses	0	0
Fair Value	$ 2,879	$ 4,081
Weighted Average Yield	3.60%	3.62%