Commitments and contingencies - Additional Information (Detail) (USD $)	3 Months Ended			6 Months Ended					3 Months Ended			4 Months Ended
	Jun. 30, 2014 D		Jun. 30, 2013	Jun. 30, 2014 D		Jun. 30, 2013	Dec. 31, 2013		Jun. 30, 2014 Pending Litigation Against Multiple Defendants [Member]	Jun. 30, 2014 Minimum Member	Jun. 30, 2014 Maximum Member	May 02, 2014 Banco Popular De Puerto Rico [Member] Arbitration With F D I C Regarding Reimbursement For Westernbank Loans [Member]	Jun. 30, 2014 Banco Popular De Puerto Rico [Member] Arbitration With F D I C Regarding Reimbursement For Westernbank Loans [Member]	Jun. 30, 2014 Credit Concentration Risk Member Government PR Government Indirect Exposure [Member] Housing Bonds backed by GNMA, FNMA or residential CMOs	Dec. 31, 2013 Credit Concentration Risk Member Government PR Government Indirect Exposure [Member] Housing Bonds backed by GNMA, FNMA or residential CMOs	Jun. 30, 2014 Credit Concentration Risk Member Government PR Government Indirect Exposure [Member] Long-term Debt [Member]	Dec. 31, 2013 Credit Concentration Risk Member Government PR Government Indirect Exposure [Member] Long-term Debt [Member]	Jun. 30, 2014 Credit Concentration Risk Member Outstanding Balance [Member] Government PR Government Direct Exposure [Member]	Dec. 31, 2013 Credit Concentration Risk Member Outstanding Balance [Member] Government PR Government Direct Exposure [Member]	Jun. 30, 2014 Credit Concentration Risk Member Outstanding Balance [Member] Government PR Government Direct Exposure [Member] From PR Government And Public Corporations [Member]	Dec. 31, 2013 Credit Concentration Risk Member Outstanding Balance [Member] Government PR Government Direct Exposure [Member] From PR Government And Public Corporations [Member]	Jun. 30, 2014 Credit Concentration Risk Member Outstanding Balance [Member] Government PR Government Direct Exposure [Member] From Municipalities [Member]	Dec. 31, 2013 Credit Concentration Risk Member Outstanding Balance [Member] Government PR Government Direct Exposure [Member] From Municipalities [Member]	Jun. 30, 2014 Credit Concentration Risk Member Outstanding Balance [Member] Government PR Government Indirect Exposure [Member]	Dec. 31, 2013 Credit Concentration Risk Member Outstanding Balance [Member] Government PR Government Indirect Exposure [Member]	Jun. 30, 2014 Credit Concentration Risk Member Total [Member] Government PR Government Direct Exposure [Member]	Dec. 31, 2013 Credit Concentration Risk Member Total [Member] Government PR Government Direct Exposure [Member]	Jun. 30, 2014 Credit Concentration Risk Member Total [Member] Government PR Government Indirect Exposure [Member]	Dec. 31, 2013 Credit Concentration Risk Member Total [Member] Government PR Government Indirect Exposure [Member]	Jun. 30, 2014 Commitments To Extend Credit Member	Dec. 31, 2013 Commitments To Extend Credit Member
Commitments and Contingencies Disclosure [Line Items]
Reserve of potential losses associated with unfunded loan commitments																														$ 6,000,000	$ 7,000,000
Unrecorded Unconditional Purchase Obligation Balance Sheet Amount	10,000,000			10,000,000			10,000,000
Estimate of possible loss	128,000,000			128,000,000			128,000,000
Concentration Of Risk Credit Facilities														48,000,000	52,000,000	33,000,000	34,000,000	709,000,000	950,000,000	272,000,000	527,000,000	437,000,000	423,000,000			833,000,000	1,200,000,000	360,000,000	360,000,000
True Up Payment Term	45			45
Loss Contingency Range Of Possible Loss Portion Not Accrued										0	43,500,000
Loans and Leases Receivable, Consumer, Mortgage with PRHA																								279,000,000	274,000,000
F D I C Indemnification Asset Cash Payments Received	(31,530,000)		0	(112,857,000)		107,000						66,300,000
Total Unreimbursed F D I C Shared Loss Claims												303,100,000	369,400,000
Methodology Computation Charge Offs												156,600,000
Loans And Leases Receivable Net Of Deferred Income	19,635,224,000	[1]		19,635,224,000	[1]		21,611,866,000	[1]										570,000,000	789,000,000
Investments																		139,000,000	161,000,000
Loss Contingency Aggregate Claims Damages Sought									60,000,000
Loss Contingency Claim Damages Sought									$ 71,500,000

[1] Non-covered loans held-in-portfolio at June 30, 2014 are net of $91 million in unearned income and exclude $97 million in loans held-for-sale. (December 31, 2013 - $92 million in unearned income and $110 million in loans held-for-sale.)