Fair value and gross unrealized losses of investment securities available-for-sale, aggregated by investment category and length of time individual securities have been in a continuous unrealized loss position (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	$ 3,259,412	$ 3,055,888
Less than 12 months Gross Unrealized Losses	79,757	119,453
12 months or more Fair Value	301,467	190,985
12 months or more Gross Unrealized Losses	24,039	10,981
Total Fair Value	3,560,879	3,246,873
Total Gross Unrealized Losses	103,796	130,434
US Government Sponsored Enterprises Debt Securities Member
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	1,766,585	1,326,866
Less than 12 months Gross Unrealized Losses	26,910	32,457
12 months or more Fair Value	22,815	69,257
12 months or more Gross Unrealized Losses	650	4,240
Total Fair Value	1,789,400	1,396,123
Total Gross Unrealized Losses	27,560	36,697
Puerto Rico States And Political Subdivisions Debt Securities [Member]
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	29,571	54,256
Less than 12 months Gross Unrealized Losses	456	11,685
12 months or more Fair Value	35,089	8,330
12 months or more Gross Unrealized Losses	8,479	190
Total Fair Value	64,660	62,586
Total Gross Unrealized Losses	8,935	11,875
Collateralized Mortgage Obligations Issued By U S Government Sponsored Enterprises And U S Government [Member]
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	1,387,656	1,567,654
Less than 12 months Gross Unrealized Losses	49,496	70,378
12 months or more Fair Value	220,582	96,676
12 months or more Gross Unrealized Losses	13,630	5,645
Total Fair Value	1,608,238	1,664,330
Total Gross Unrealized Losses	63,126	76,023
Collateralized Mortgage Obligations Issued By Private Enterprise [Member]
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	0	0
Less than 12 months Gross Unrealized Losses	0	0
12 months or more Fair Value	0	0
12 months or more Gross Unrealized Losses	0	0
Total Fair Value	0	0
Total Gross Unrealized Losses	0	0
Collateralized Mortgage Backed Securities [Member]
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	75,600	105,455
Less than 12 months Gross Unrealized Losses	2,895	4,762
12 months or more Fair Value	11,817	7,225
12 months or more Gross Unrealized Losses	1,070	765
Total Fair Value	87,417	112,680
Total Gross Unrealized Losses	3,965	5,527
Equity Securities [Member]
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	0	1,657
Less than 12 months Gross Unrealized Losses	0	171
12 months or more Fair Value	1,692	0
12 months or more Gross Unrealized Losses	135	0
Total Fair Value	1,692	1,657
Total Gross Unrealized Losses	135	171
Other Securities [Member]
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	0	0
Less than 12 months Gross Unrealized Losses	0	0
12 months or more Fair Value	9,472	9,497
12 months or more Gross Unrealized Losses	75	141
Total Fair Value	9,472	9,497
Total Gross Unrealized Losses	$ 75	$ 141