Fair Value and Gross Unrealized Losses of Investment Securities Held-To-Maturity, Aggregated by Investment Category and Length of Time Individual Securities Have Been in a Continuous Unrealized Loss Position (Detail) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2010
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	$ 15,820	$ 78,110
Less than 12 months Gross Unrealized Losses	270	1,923
12 months or more Fair Value	31,265	939	45,657
12 months or more Gross Unrealized Losses	731	12	1,087
Total Fair Value	47,085	79,049	45,657
Total Gross Unrealized Losses	1,001	1,935	1,087
Obligations of Puerto Rico, States and political subdivisions
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	15,820	51,995
Less than 12 months Gross Unrealized Losses	270	1,915
12 months or more Fair Value	31,108	773	45,460
12 months or more Gross Unrealized Losses	722	2	1,075
Total Fair Value	46,928	52,768	45,460
Total Gross Unrealized Losses	992	1,917	1,075
Collateralized mortgage obligations - private label
Investments, Unrealized Loss Position [Line Items]
12 months or more Fair Value	157	166	197
12 months or more Gross Unrealized Losses	9	10	12
Total Fair Value	157	166	197
Total Gross Unrealized Losses	9	10	12
U.S. Treasury securities
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value		25,872
Less than 12 months Gross Unrealized Losses		1
Total Fair Value		25,872
Total Gross Unrealized Losses		1
Other
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value		243
Less than 12 months Gross Unrealized Losses		7
Total Fair Value		243
Total Gross Unrealized Losses		$ 7