Allowance for loan losses - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011	Dec. 31, 2010
Financing Receivable, Modifications [Line Items]
Allowance for loan losses	$ 803,264,000	$ 815,308,000	$ 736,505,000	$ 793,225,000
Financing Receivable Modifications Recorded Investment	911,000,000	881,000,000
Financing Receivable Credit Quality Additional Information	Risk ratings scales 10 through 14 conform to regulatory ratings. The assignment of the obligor risk rating is based on relevant information about the ability of borrowers to service their debts such as current financial information, historical payment experience, credit documentation, public information, and current economic trends, among other factors.
Credit Card T D R Modification Time Period	24
Historical Loss Window Commercial Construction	3
Historical Loss Window Consumer Mortgage	18
Trend Factor Base Loss Commercial Construction Legacy	12
Trend Factor Base Loss Consumer Mortgage	6
Change Allowance For Loan Losses Change In Methodology	40,500,000
Change Allowance For Loan Losses Loan Groupings	7,900,000
Look Back Period Recent Trends Previous	6
Look Back Period Recent Trends Current	12
Change Allowance For Loan Losses Look Back Period	28,100,000
Change Allowance For Loan Losses Additional Enhancements	4,500,000
Change Due Environmental Factor Reserves	15,700,000
Net Impact Revisions	24,800,000
Banco Popular De Puerto Rico [Member]
Financing Receivable, Modifications [Line Items]
Change Allowance For Loan Losses Loan Groupings	1,800,000
Change Allowance For Loan Losses Look Back Period	24,000,000
Change Allowance For Loan Losses Additional Enhancements	600,000
Banco Popular North America [Member]
Financing Receivable, Modifications [Line Items]
Change Allowance For Loan Losses Loan Groupings	9,700,000
Change Allowance For Loan Losses Look Back Period	4,100,000
Change Allowance For Loan Losses Additional Enhancements	3,900,000
Covered Under Loss Sharing Agreements With F D I C [Member]
Financing Receivable, Modifications [Line Items]
Allowance for loan losses	138,496,000	124,945,000	4,729,550,000
Commercial Real Estate Construction Financing Receivable Member
Financing Receivable, Modifications [Line Items]
Allowance for loan losses	38,860,000	28,916,000	40,511,000	39,785,000
Commercial Real Estate Construction Financing Receivable Member | Covered Under Loss Sharing Agreements With F D I C [Member]
Financing Receivable, Modifications [Line Items]
Allowance for loan losses	29,727,000	20,435,000	621,187,000
Commercial Portfolio Segment Member
Financing Receivable, Modifications [Line Items]
Allowance for loan losses	403,649,000	463,904,000	349,226,000	399,924,000
Commercial Portfolio Segment Member | Covered Under Loss Sharing Agreements With F D I C [Member]
Financing Receivable, Modifications [Line Items]
Allowance for loan losses	90,070,000	94,472,000	1,935,000
Loans | Covered Under Loss Sharing Agreements With F D I C [Member] | Westernbank Puerto Rico [Member]
Financing Receivable, Modifications [Line Items]
Allowance for loan losses		125,000,000
Loans | Covered Under Loss Sharing Agreements With F D I C [Member] | Westernbank Puerto Rico [Member] | A S C Subtopic 31020 [Member]
Financing Receivable, Modifications [Line Items]
Allowance for loan losses	42,000,000
Loans | Covered Under Loss Sharing Agreements With F D I C [Member] | Westernbank Puerto Rico [Member] | A S C Subtopic 31030 [Member]
Financing Receivable, Modifications [Line Items]
Allowance for loan losses	83,000,000
Loans | Commercial Real Estate Construction Financing Receivable Member
Financing Receivable, Modifications [Line Items]
Loans And Leases Receivable Impaired Commitment To Lend	445,000	152,000
Loans | Commercial Portfolio Segment Member
Financing Receivable, Modifications [Line Items]
Loans And Leases Receivable Impaired Commitment To Lend	$ 3,000,000	$ 3,000,000