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	Sep. 30, 2013	Dec. 31, 2012
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	$ 2,557,354	$ 332,839
Less than 12 months Gross Unrealized Losses	96,243	1,445
12 months or more Fair Value	60,532	3,065
12 months or more Gross Unrealized Losses	2,971	80
Total Fair Value	2,617,886	335,904
Total Gross Unrealized Losses	99,214	1,525
US Government Sponsored Enterprises Debt Securities Member
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	999,439	139,278
Less than 12 months Gross Unrealized Losses	25,867	592
12 months or more Fair Value	3,252	0
12 months or more Gross Unrealized Losses	185	0
Total Fair Value	1,002,691	139,278
Total Gross Unrealized Losses	26,052	592
Puerto Rico States And Political Subdivisions Debt Securities [Member]
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	50,477	6,229
Less than 12 months Gross Unrealized Losses	12,683	44
12 months or more Fair Value	1,971	2,031
12 months or more Gross Unrealized Losses	74	31
Total Fair Value	52,448	8,260
Total Gross Unrealized Losses	12,757	75
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	1,439,297	170,136
Less than 12 months Gross Unrealized Losses	53,316	512
12 months or more Fair Value	54,407	0
12 months or more Gross Unrealized Losses	2,679	0
Total Fair Value	1,493,704	170,136
Total Gross Unrealized Losses	55,995	512
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	57,035	7,411
Less than 12 months Gross Unrealized Losses	3,928	90
12 months or more Fair Value	902	983
12 months or more Gross Unrealized Losses	33	39
Total Fair Value	57,937	8,394
Total Gross Unrealized Losses	3,961	129
Equity Securities [Member]
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	1,642	0
Less than 12 months Gross Unrealized Losses	186	0
12 months or more Fair Value	0	51
12 months or more Gross Unrealized Losses	0	10
Total Fair Value	1,642	51
Total Gross Unrealized Losses	186	10
Other Securities [Member]
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	9,464	9,785
Less than 12 months Gross Unrealized Losses	263	207
12 months or more Fair Value	0	0
12 months or more Gross Unrealized Losses	0	0
Total Fair Value	9,464	9,785
Total Gross Unrealized Losses	$ 263	$ 207