Income Taxes - Additional Information (Detail) (USD $)	3 Months Ended					3 Months Ended		9 Months Ended		12 Months Ended	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011	Sep. 30, 2012 Other Liabilities Member	Dec. 31, 2011 Other Liabilities Member	Sep. 30, 2012 PUERTO RICO	Sep. 30, 2011 PUERTO RICO	Sep. 30, 2012 PUERTO RICO	Sep. 30, 2011 PUERTO RICO	Dec. 31, 2010 PUERTO RICO	Sep. 30, 2012 PUERTO RICO Westernbank Assets Capital Gain Treatment [Member]	Jun. 30, 2012 PUERTO RICO Westernbank Assets Capital Gain Treatment [Member]	Sep. 30, 2012 PUERTO RICO Commercial Banking [Member]
Income Taxes [Line Items]
Income Tax Reconciliation Prior Year Income Taxes									$ 53,600,000
Income Tax Reconciliation Change In Enacted Tax Rate								0	103,287,000
Marginal Income Tax Rate								30.00%		39.00%	30.00%
Deferred Tax Assets Net	545,859,000	429,691,000				561,000,000		561,000,000
Deferred Tax Liabilities	167,712,000	279,789,000		11,000,000	25,000,000
Income Tax Examination Minimum Likelihood Of Tax Benefits Being Realized Upon Ultimate Settlement	50.00%
Deferred Tax Assets Valuation Allowance	1,261,594,000	1,259,358,000
Unrecognized Tax Benefits Interest On Income Taxes Accrued	4,100,000	5,500,000
Income Tax Examination Penalties Accrued	0	0
Unrecognized Tax Benefits That Would Impact Effective Tax Rate	16,400,000		25,600,000
Significant Change In Unrecognized Tax Benefits Is Reasonably Possible Amount Of Unrecorded Benefit	8,000,000
Effective Income Tax Rate Continuing Operations						25.00%	17.00%	(40.00%)	44.00%				15.80%
Preferential Tax Rate											15.00%
Prepaid Taxes	$ 99,500,000	$ 17,441,000										$ 72,900,000