Selected Balance Sheet information (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011
Segment Reporting Information [Line Items]
Total assets	$ 37,049,221	$ 37,348,432	$ 38,829,793
Deposits	27,197,736	27,942,127	27,196,674
PUERTO RICO
Segment Reporting Information [Line Items]
Total assets	26,980,854	27,410,644	28,582,499
Loans	18,482,906	18,594,751	18,723,166
Deposits	19,915,877	20,696,606	19,524,566
UNITED STATES
Segment Reporting Information [Line Items]
Total assets	8,829,183	8,708,709	9,098,562
Loans	5,707,884	5,845,359	6,483,596
Deposits	6,240,063	6,151,959	6,570,511
Other
Segment Reporting Information [Line Items]
Total assets	1,239,184	1,229,079	1,148,732
Loans	871,268	874,282	769,255
Deposits	$ 1,041,796	$ 1,093,562	$ 1,101,597