Activity in Allowance for Loan Losses Related to ASC 310-30 Acquired Loans (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at beginning of period	$ 766,030	$ 746,847	$ 815,308	$ 793,225
Provision for loan losses	106,208	176,276	326,130	395,912
Charge-offs	(144,323)	(176,636)	(479,007)	(519,586)
Balance at end of period	761,172	772,921	761,172	772,921
Westernbank Puerto Rico [Member] | Acquired Loans In An F D I C Assisted Transaction [Member] | Nonperforming Financing Receivable Member
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at beginning of period	93,971	48,257	83,477	0
Provision for loan losses	17,881	15,920	57,472	68,602
Charge-offs	(8,305)	(1,731)	(37,402)	(6,156)
Balance at end of period	$ 103,547	$ 62,446	$ 103,547	$ 62,446