Allowance for Loan Losses - Additional Information (Detail) (USD $)								3 Months Ended
	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Jun. 30, 2011 Commercial Loans	Dec. 31, 2010 Commercial Loans	Jun. 30, 2011 Construction Loans	Dec. 31, 2010 Construction Loans	Jun. 30, 2011 Loans	Dec. 31, 2010 Loans	Jun. 30, 2011 Construction	Mar. 31, 2011 Construction	Dec. 31, 2010 Construction	Jun. 30, 2011 Commercial	Mar. 31, 2011 Commercial	Dec. 31, 2010 Commercial	Jun. 30, 2011 Covered under Loss Sharing Agreements with FDIC Westernbank Puerto Rico	Jun. 30, 2011 Covered under Loss Sharing Agreements with FDIC Westernbank Puerto Rico ASC Subtopic 310 30	Jun. 30, 2011 Covered under Loss Sharing Agreements with FDIC Westernbank Puerto Rico ASC Subtopic 310 20
Financing Receivable, Modifications [Line Items]
Allowance for loan losses	$ 746,847,000	$ 736,505,000	$ 793,225,000							$ 29,076,000	$ 46,138,000	$ 47,724,000	$ 459,594,000	$ 409,775,000	$ 462,391,000	$ 57,000,000	$ 9,000,000	$ 48,000,000
Troubled debt restructurings								673,000,000	561,000,000
Outstanding commitments to lend additional funds to debtors owing receivables whose terms have been modified in troubled debt restructurings				$ 1,000,000	$ 1,000,000	$ 486,000	$ 3,000,000
Loans receivable credit quality, rating description								The Corporation’s obligor risk rating scales range from rating 1 (Excellent) to rating 14 (Loss). The obligor risk rating reflects the risk of payment default of a borrower in the ordinary course of business.