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, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 4,872,157	$ 4,779,077
Gross Unrealized Gains	207,811	238,461
Gross Unrealized Losses	3,171	7,715
Fair Value	5,076,797	5,009,823
Weighted Average Yield	3.31%	3.58%
US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	34,623	34,980
Gross Unrealized Gains	3,305	3,688
Gross Unrealized Losses	0	0
Fair Value	37,928	38,668
Weighted Average Yield	3.35%	3.35%
US Treasury Securities [Member] | One Year From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	7,014	0
Gross Unrealized Gains	64	0
Gross Unrealized Losses	0	0
Fair Value	7,078	0
Weighted Average Yield	1.50%	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	27,609	34,980
Gross Unrealized Gains	3,241	3,688
Gross Unrealized Losses	0	0
Fair Value	30,850	38,668
Weighted Average Yield	3.82%	3.35%
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	1,017,262	953,836
Gross Unrealized Gains	22,309	31,710
Gross Unrealized Losses	173	0
Fair Value	1,039,398	985,546
Weighted Average Yield	2.96%	3.30%
US Government Sponsored Enterprises Debt Securities Member | One Year From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	539,045	94,492
Gross Unrealized Gains	16,168	2,382
Gross Unrealized Losses	0	0
Fair Value	555,213	96,874
Weighted Average Yield	3.84%	3.45%
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	190,538	655,625
Gross Unrealized Gains	2,646	25,860
Gross Unrealized Losses	7	0
Fair Value	193,177	681,485
Weighted Average Yield	1.81%	3.38%
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	280,596	171,633
Gross Unrealized Gains	3,206	2,969
Gross Unrealized Losses	166	0
Fair Value	283,636	174,602
Weighted Average Yield	1.98%	2.94%
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	7,083	32,086
Gross Unrealized Gains	289	499
Gross Unrealized Losses	0	0
Fair Value	7,372	32,585
Weighted Average Yield	5.41%	3.20%
Obligations of Puerto Rico, States and political subdivisions
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	48,882	57,504
Gross Unrealized Gains	1,061	1,255
Gross Unrealized Losses	34	31
Fair Value	49,909	58,728
Weighted Average Yield	5.04%	5.03%
Obligations of Puerto Rico, States and political subdivisions | One Year From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,000	765
Gross Unrealized Gains	54	9
Gross Unrealized Losses	0	0
Fair Value	5,054	774
Weighted Average Yield	2.99%	4.97%
Obligations of Puerto Rico, States and political subdivisions | More Than One And Within Five Years From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	6,592	14,824
Gross Unrealized Gains	199	283
Gross Unrealized Losses	34	31
Fair Value	6,757	15,076
Weighted Average Yield	4.67%	4.07%
Obligations of Puerto Rico, States and political subdivisions | More Than Five And Within Ten Years From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	0	4,595
Gross Unrealized Gains	0	54
Gross Unrealized Losses	0	0
Fair Value	0	4,649
Weighted Average Yield	0.00%	5.33%
Obligations of Puerto Rico, States and political subdivisions | More Than Ten Years From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	37,290	37,320
Gross Unrealized Gains	808	909
Gross Unrealized Losses	0	0
Fair Value	38,098	38,229
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	1,952,630	1,646,893
Gross Unrealized Gains	49,270	50,957
Gross Unrealized Losses	318	208
Fair Value	2,001,582	1,697,642
Weighted Average Yield	2.53%	2.83%
Collateralized Mortgage Obligations Issued By U S Government Sponsored Enterprises And U S Government [Member] | 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	6,130	2,424
Gross Unrealized Gains	62	49
Gross Unrealized Losses	0	0
Fair Value	6,192	2,473
Weighted Average Yield	1.52%	3.28%
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	37,137	55,096
Gross Unrealized Gains	1,580	1,446
Gross Unrealized Losses	0	0
Fair Value	38,717	56,542
Weighted Average Yield	2.85%	2.64%
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	1,909,363	1,589,373
Gross Unrealized Gains	47,628	49,462
Gross Unrealized Losses	318	208
Fair Value	1,956,673	1,638,627
Weighted Average Yield	2.53%	2.84%
Collateralized Mortgage Obligations Issued By Private Enterprise [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	42,763	65,113
Gross Unrealized Gains	45	1
Gross Unrealized Losses	2,474	7,322
Fair Value	40,334	57,792
Weighted Average Yield	2.70%	2.30%
Collateralized Mortgage Obligations Issued By Private Enterprise [Member] | 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	41	5,653
Gross Unrealized Gains	2	1
Gross Unrealized Losses	0	181
Fair Value	43	5,473
Weighted Average Yield	4.95%	0.81%
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	42,722	59,460
Gross Unrealized Gains	43	0
Gross Unrealized Losses	2,474	7,141
Fair Value	40,291	52,319
Weighted Average Yield	2.70%	2.44%
Collateralized Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,746,470	1,989,996
Gross Unrealized Gains	129,290	149,623
Gross Unrealized Losses	34	50
Fair Value	1,875,726	2,139,569
Weighted Average Yield	4.26%	4.27%
Collateralized Mortgage Backed Securities [Member] | One Year From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	689	57
Gross Unrealized Gains	26	1
Gross Unrealized Losses	0	0
Fair Value	715	58
Weighted Average Yield	3.79%	3.91%
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	4,880	7,564
Gross Unrealized Gains	228	328
Gross Unrealized Losses	0	0
Fair Value	5,108	7,892
Weighted Average Yield	3.93%	3.86%
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	95,331	111,639
Gross Unrealized Gains	7,272	8,020
Gross Unrealized Losses	0	1
Fair Value	102,603	119,658
Weighted Average Yield	4.68%	4.66%
Collateralized Mortgage Backed Securities [Member] | More Than Ten Years From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,645,570	1,870,736
Gross Unrealized Gains	121,764	141,274
Gross Unrealized Losses	34	49
Fair Value	1,767,300	2,011,961
Weighted Average Yield	4.24%	4.25%
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	6,595	6,594
Gross Unrealized Gains	565	426
Gross Unrealized Losses	138	104
Fair Value	7,022	6,916
Weighted Average Yield	3.05%	2.96%
Other
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	22,932	24,161
Gross Unrealized Gains	1,966	801
Gross Unrealized Losses	0	0
Fair Value	24,898	24,962
Weighted Average Yield	9.41%	9.06%
Other | 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 | 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%
Other | More Than Five And Within Ten Years From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	18,025	17,850
Gross Unrealized Gains	1,838	700
Gross Unrealized Losses	0	0
Fair Value	19,863	18,550
Weighted Average Yield	10.99%	10.99%
Other | More Than Ten Years From Balance Sheet Date [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,907	6,311
Gross Unrealized Gains	128	101
Gross Unrealized Losses	0	0
Fair Value	$ 5,035	$ 6,412
Weighted Average Yield	3.62%	3.61%