Commitments and contingencies - Additional Information (Detail) (USD $)																								3 Months Ended		3 Months Ended	12 Months Ended				12 Months Ended		3 Months Ended	12 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011	Mar. 31, 2012 Minimum Member	Mar. 31, 2012 Maximum Member	Mar. 31, 2012 Credit Concentration Risk Member Obligations of Puerto Rico, States and political subdivisions	Dec. 31, 2011 Credit Concentration Risk Member Obligations of Puerto Rico, States and political subdivisions	Mar. 31, 2011 Credit Concentration Risk Member Obligations of Puerto Rico, States and political subdivisions	Mar. 31, 2012 Credit Concentration Risk Member Commercial Real Estate Portfolio Segment Member	Dec. 31, 2011 Credit Concentration Risk Member Commercial Real Estate Portfolio Segment Member	Mar. 31, 2011 Credit Concentration Risk Member Commercial Real Estate Portfolio Segment Member	Mar. 31, 2012 Credit Concentration Risk Member Other Credit Facilities [Member]	Dec. 31, 2011 Credit Concentration Risk Member Other Credit Facilities [Member]	Mar. 31, 2011 Credit Concentration Risk Member Other Credit Facilities [Member]	Mar. 31, 2012 Credit Concentration Risk Member Uncommitted Credit Facility [Member]	Dec. 31, 2011 Credit Concentration Risk Member Uncommitted Credit Facility [Member]	Mar. 31, 2011 Credit Concentration Risk Member Uncommitted Credit Facility [Member]	Mar. 31, 2012 Commitments To Extend Credit Member Line Of Credit Member Covered Under Loss Sharing Agreements With F D I C [Member]	Dec. 31, 2011 Commitments To Extend Credit Member Line Of Credit Member Covered Under Loss Sharing Agreements With F D I C [Member]	Mar. 31, 2011 Commitments To Extend Credit Member Line Of Credit Member Covered Under Loss Sharing Agreements With F D I C [Member]	Mar. 31, 2012 Commitments To Extend Credit Member Reserve For Off Balance Sheet Activities [Member] Line Of Credit Member	Dec. 31, 2011 Commitments To Extend Credit Member Reserve For Off Balance Sheet Activities [Member] Line Of Credit Member	Mar. 31, 2011 Commitments To Extend Credit Member Reserve For Off Balance Sheet Activities [Member] Line Of Credit Member	Mar. 31, 2012 Putative Class Action [Member]	Dec. 31, 2011 Putative Class Action [Member]	Mar. 31, 2012 Derivative Claim [Member]	Dec. 31, 2010 Securities Class Action [Member] Banco Popular De Puerto Rico [Member]	Dec. 31, 2011 Hoff Vs Popular [Member] Parent Company [Member]	Dec. 31, 2011 Hoff Vs Popular [Member] Insurance Settlement [Member]	Dec. 31, 2011 Hoff Vs Popular [Member] Insurance Settlement [Member] Parent Company [Member]	Dec. 31, 2011 Employee Retirement Income Security Act E R I S A Class Action [Member] Parent Company [Member]	Dec. 31, 2011 Employee Retirement Income Security Act E R I S A Class Action [Member] Insurance Settlement [Member]	Mar. 31, 2012 Consumer Banking And Trust Related Activities [Member]	Dec. 31, 2011 Legal Claim Garcia And Diaz [Member]
Commitments and Contingencies Disclosure [Line Items]
Reserve of potential losses associated with unfunded loan commitments																					$ 9,000,000	$ 15,000,000	$ 17,000,000
Fair Value Disclosure Offbalance Sheet Risks Face Amount Liability																		3,000,000	5,000,000	4,000,000
Unrecorded Unconditional Purchase Obligation Balance Sheet Amount	10,000,000	10,000,000	10,000,000
Estimate of possible loss	100,000,000	98,000,000	94,000,000
Fair Value Concentration Of Risk Loans Receivable						151,000,000	154,000,000	143,000,000	12,400,000,000	12,500,000,000	12,200,000,000	863,000,000	1,200,000,000	1,100,000,000	264,000,000	140,000,000	215,000,000
Concentration Risk Percentage									61.00%	61.00%	59.00%
Fair Value Concentration Of Risk Credit Facilities Granted												1,100,000,000	1,300,000,000	1,400,000,000
Loss Contingency Range Of Possible Loss Portion Not Accrued				0	16,500,000
Loss Contingency New Claims Filed Number																								5		2							2
Legal Proceedings, amount paid to the settlement fund																												11,500,000
Amount Reimbursed By Insurers																													4,700,000
Legal Fees																																		2,100,000
Estimated Insurance Recoveries																														26,000,000		8,200,000
Estimate of possible loss																									400,000
Legal Proceedings, amount paid to the settlement fund																												37,500,000			8,200,000
Loss Contingency Damages Sought Value																											600,000,000
Litigation Settlement, Gross																												$ 37,500,000