Activity in Allowance for Loan Losses Related to ASC 310-30 Acquiered Loans (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at beginning of period	$ 815,308	$ 793,225
Provision for loan losses	100,723	75,319
Charge-offs	(144,689)	(171,101)
Balance at end of period	803,264	736,505
Westernbank Puerto Rico [Member] | Acquired Loans In An F D I C Assisted Transaction [Member] | Credit Impaired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at beginning of period	83,477	0
Provision for loan losses	11,370	9,127
Charge-offs	(288)	(3,830)
Balance at end of period	$ 94,559	$ 5,297