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	Jun. 30, 2013	Dec. 31, 2012
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	$ 2,604,476	$ 332,839
Less than 12 months Gross Unrealized Losses	71,301	1,445
12 months or more Fair Value	9,003	3,065
12 months or more Gross Unrealized Losses	419	80
Total Fair Value	2,613,479	335,904
Total Gross Unrealized Losses	71,720	1,525
US Government Sponsored Enterprises Debt Securities Member
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	978,478	139,278
Less than 12 months Gross Unrealized Losses	29,462	592
12 months or more Fair Value	6,024	0
12 months or more Gross Unrealized Losses	354	0
Total Fair Value	984,502	139,278
Total Gross Unrealized Losses	29,816	592
Puerto Rico States And Political Subdivisions Debt Securities [Member]
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	40,588	6,229
Less than 12 months Gross Unrealized Losses	1,972	44
12 months or more Fair Value	2,025	2,031
12 months or more Gross Unrealized Losses	25	31
Total Fair Value	42,613	8,260
Total Gross Unrealized Losses	1,997	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	1,513,901	170,136
Less than 12 months Gross Unrealized Losses	35,720	512
12 months or more Fair Value	0	0
12 months or more Gross Unrealized Losses	0	0
Total Fair Value	1,513,901	170,136
Total Gross Unrealized Losses	35,720	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	60,331	7,411
Less than 12 months Gross Unrealized Losses	3,682	90
12 months or more Fair Value	908	983
12 months or more Gross Unrealized Losses	36	39
Total Fair Value	61,239	8,394
Total Gross Unrealized Losses	3,718	129
Equity Securities [Member]
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	1,779	0
Less than 12 months Gross Unrealized Losses	49	0
12 months or more Fair Value	46	51
12 months or more Gross Unrealized Losses	4	10
Total Fair Value	1,825	51
Total Gross Unrealized Losses	53	10
Other Securities [Member]
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	9,399	9,785
Less than 12 months Gross Unrealized Losses	416	207
12 months or more Fair Value	0	0
12 months or more Gross Unrealized Losses	0	0
Total Fair Value	9,399	9,785
Total Gross Unrealized Losses	$ 416	$ 207