Note Commitments and contingencies (Commitments) - Additional Information (Detail) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2016 USD ($) D		Dec. 31, 2015 USD ($)
Commitments and Contingencies Disclosure [Line Items]
Unrecorded Unconditional Purchase Obligation Balance Sheet Amount	$ 9,000		$ 9,000
True Up Payment Term | D	45
Loans And Leases Receivable Net Of Deferred Income	$ 22,507,737	[1],[2]	22,346,115	[3],[4]
PR Government Direct Exposure
Commitments and Contingencies Disclosure [Line Items]
Concentration Risk Credit Risk Financial Instrument Maximum Exposure	656,165		669,337
PR Government Direct Exposure | From PR Government And Public Corporations
Commitments and Contingencies Disclosure [Line Items]
Concentration Of Risk Credit Facilities	60,478		75,858
PR Government Direct Exposure | From Municipalities
Commitments and Contingencies Disclosure [Line Items]
Concentration Of Risk Credit Facilities	504,389		501,901
Concentration Risk Credit Risk Financial Instrument Maximum Exposure	517,707
PR Government Direct Exposure | From Public Corporation - Puerto Rico Electric Power Authority [Member]
Commitments and Contingencies Disclosure [Line Items]
Concentration Risk Credit Risk Financial Instrument Maximum Exposure	40,936
PR Government Indirect Exposure
Commitments and Contingencies Disclosure [Line Items]
Concentration Of Risk Credit Facilities	417,000		394,000
PR Government Indirect Exposure | Housing Bonds backed by GNMA, FNMA or residential CMOs
Commitments and Contingencies Disclosure [Line Items]
Concentration Of Risk Credit Facilities	51,000		50,000
PR Government Indirect Exposure | Commercial real estate
Commitments and Contingencies Disclosure [Line Items]
Concentration Of Risk Credit Facilities	27,000		28,000
Outstanding Balance | PR Government Direct Exposure
Commitments and Contingencies Disclosure [Line Items]
Concentration Of Risk Credit Facilities	564,867		577,759
Outstanding Balance | PR Government Direct Exposure | From Municipalities
Commitments and Contingencies Disclosure [Line Items]
Concentration Of Risk Credit Facilities	504,389
Outstanding Balance | PR Government Direct Exposure | From Public Corporation - Puerto Rico Electric Power Authority [Member]
Commitments and Contingencies Disclosure [Line Items]
Concentration Of Risk Credit Facilities	40,936
Outstanding Balance | PR Government Indirect Exposure
Commitments and Contingencies Disclosure [Line Items]
Loans and Leases Receivable, Consumer, Mortgage with PRHA	339,000		316,000
Commitments To Extend Credit
Commitments and Contingencies Disclosure [Line Items]
Reserve of potential losses associated with unfunded loan commitments	10,000		10,000
Loans | Outstanding Balance | PR Government Direct Exposure
Commitments and Contingencies Disclosure [Line Items]
Concentration Of Risk Credit Facilities	490,363		502,251
Loans | Outstanding Balance | PR Government Direct Exposure | From Municipalities
Commitments and Contingencies Disclosure [Line Items]
Concentration Of Risk Credit Facilities	449,449
Loans | Outstanding Balance | PR Government Direct Exposure | From Public Corporation - Puerto Rico Electric Power Authority [Member]
Commitments and Contingencies Disclosure [Line Items]
Concentration Of Risk Credit Facilities	40,914
Securities Investment | Outstanding Balance | PR Government Direct Exposure
Commitments and Contingencies Disclosure [Line Items]
Concentration Of Risk Credit Facilities	74,504		$ 75,508
Securities Investment | Outstanding Balance | PR Government Direct Exposure | From Municipalities
Commitments and Contingencies Disclosure [Line Items]
Concentration Of Risk Credit Facilities	54,940
Securities Investment | Outstanding Balance | PR Government Direct Exposure | From Public Corporation - Puerto Rico Electric Power Authority [Member]
Commitments and Contingencies Disclosure [Line Items]
Concentration Of Risk Credit Facilities	$ 22

[1] Includes $7.7 billion pledged to secure credit facilities and public funds that the secured parties are not permitted to sell or repledge the collateral, of which $4.7 billion were pledged at the FHLB as collateral for borrowings, $2.5 billion at the FRB for discount window borrowings and $0.5 billion serve as collateral for public funds.

[2] Non-covered loans held-in-portfolio are net of $111 million in unearned income and exclude $125 million in loans held-for-sale.

[3] Includes $7.3 billion pledged to secure credit facilities and public funds that the secured parties are not permitted to sell or repledge the collateral, of which $4.3 billion were pledged at the FHLB as collateral for borrowings, $2.5 billion at the FRB for discount window borrowings and $0.5 billion serve as collateral for public funds.

[4] Non-covered loans held-in-portfolio are net of $108 million in unearned income and exclude $137 million in loans held-for-sale.