Loans - Amortized cost basis of collateral dependent loans by class (Details) $ in Thousands	Sep. 30, 2020 USD ($)
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	$ 29,392,510
Collateral assets
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	677,002
Real Estate
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	641,927
Auto
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Equipment
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	996
Taxi medallions
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	3,607
Accounts receivable
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	12,934
Other
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	17,538
Construction
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	936,274
Construction | Collateral assets
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	30,583
Construction | Real Estate
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	30,583
Construction | Auto
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Construction | Equipment
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Construction | Taxi medallions
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Construction | Accounts receivable
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Construction | Other
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Mortgages
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	7,924,441
Mortgages | Collateral assets
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	184,827
Mortgages | Real Estate
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	184,827
Mortgages | Auto
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Mortgages | Equipment
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Mortgages | Taxi medallions
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Mortgages | Accounts receivable
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Mortgages | Other
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Commercial | Commercial multi-family
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	1,880,915
Commercial | Commercial multi-family | Collateral assets
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	4,020
Commercial | Commercial multi-family | Real Estate
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	4,020
Commercial | Commercial multi-family | Auto
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Commercial | Commercial multi-family | Equipment
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Commercial | Commercial multi-family | Taxi medallions
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Commercial | Commercial multi-family | Accounts receivable
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Commercial | Commercial multi-family | Other
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Commercial | CRE non-owner occupied
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	4,010,155
Commercial | CRE non-owner occupied | Collateral assets
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	324,143
Commercial | CRE non-owner occupied | Real Estate
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	324,143
Commercial | CRE non-owner occupied | Auto
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Commercial | CRE non-owner occupied | Equipment
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Commercial | CRE non-owner occupied | Taxi medallions
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Commercial | CRE non-owner occupied | Accounts receivable
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Commercial | CRE non-owner occupied | Other
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Commercial | CRE owner occupied
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	1,931,401
Commercial | CRE owner occupied | Collateral assets
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	83,963
Commercial | CRE owner occupied | Real Estate
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	83,963
Commercial | CRE owner occupied | Auto
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Commercial | CRE owner occupied | Equipment
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Commercial | CRE owner occupied | Taxi medallions
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Commercial | CRE owner occupied | Accounts receivable
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Commercial | CRE owner occupied | Other
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Commercial | Commercial and Industrial
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	5,788,903
Commercial | Commercial and Industrial | Collateral assets
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	43,986
Commercial | Commercial and Industrial | Real Estate
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	8,911
Commercial | Commercial and Industrial | Auto
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Commercial | Commercial and Industrial | Equipment
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	996
Commercial | Commercial and Industrial | Taxi medallions
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	3,607
Commercial | Commercial and Industrial | Accounts receivable
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	12,934
Commercial | Commercial and Industrial | Other
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	17,538
Leasing
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	1,153,108
Consumer | Personal loans
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	1,539,547
Consumer | Personal loans | Collateral assets
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	5,480
Consumer | Personal loans | Real Estate
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	5,480
Consumer | Personal loans | Auto
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Consumer | Personal loans | Equipment
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Consumer | Personal loans | Taxi medallions
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Consumer | Personal loans | Accounts receivable
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Consumer | Personal loans | Other
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Consumer | Auto Loan
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	3,045,453
Consumer | Other
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	125,352
Puerto Rico
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	21,664,643
Puerto Rico | Collateral assets
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	662,044
Puerto Rico | Real Estate
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	630,576
Puerto Rico | Auto
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Equipment
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	996
Puerto Rico | Taxi medallions
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Accounts receivable
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	12,934
Puerto Rico | Other
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	17,538
Puerto Rico | Construction
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	196,065
Puerto Rico | Construction | Collateral assets
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	21,514
Puerto Rico | Construction | Real Estate
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	21,514
Puerto Rico | Construction | Auto
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Construction | Equipment
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Construction | Taxi medallions
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Construction | Accounts receivable
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Construction | Other
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Mortgages
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	6,826,980
Puerto Rico | Mortgages | Collateral assets
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	184,300
Puerto Rico | Mortgages | Real Estate
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	184,300
Puerto Rico | Mortgages | Auto
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Mortgages | Equipment
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Mortgages | Taxi medallions
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Mortgages | Accounts receivable
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Mortgages | Other
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Commercial | Commercial multi-family
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	144,178
Puerto Rico | Commercial | Commercial multi-family | Collateral assets
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	2,265
Puerto Rico | Commercial | Commercial multi-family | Real Estate
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	2,265
Puerto Rico | Commercial | Commercial multi-family | Auto
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Commercial | Commercial multi-family | Equipment
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Commercial | Commercial multi-family | Taxi medallions
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Commercial | Commercial multi-family | Accounts receivable
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Commercial | Commercial multi-family | Other
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Commercial | CRE non-owner occupied
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	2,071,142
Puerto Rico | Commercial | CRE non-owner occupied | Collateral assets
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	324,143
Puerto Rico | Commercial | CRE non-owner occupied | Real Estate
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	324,143
Puerto Rico | Commercial | CRE non-owner occupied | Auto
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Commercial | CRE non-owner occupied | Equipment
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Commercial | CRE non-owner occupied | Taxi medallions
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Commercial | CRE non-owner occupied | Accounts receivable
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Commercial | CRE non-owner occupied | Other
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Commercial | CRE owner occupied
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	1,570,275
Puerto Rico | Commercial | CRE owner occupied | Collateral assets
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	83,963
Puerto Rico | Commercial | CRE owner occupied | Real Estate
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	83,963
Puerto Rico | Commercial | CRE owner occupied | Auto
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Commercial | CRE owner occupied | Equipment
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Commercial | CRE owner occupied | Taxi medallions
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Commercial | CRE owner occupied | Accounts receivable
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Commercial | CRE owner occupied | Other
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Commercial | Commercial and Industrial
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	4,291,752
Puerto Rico | Commercial | Commercial and Industrial | Collateral assets
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	40,379
Puerto Rico | Commercial | Commercial and Industrial | Real Estate
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	8,911
Puerto Rico | Commercial | Commercial and Industrial | Auto
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Commercial | Commercial and Industrial | Equipment
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	996
Puerto Rico | Commercial | Commercial and Industrial | Taxi medallions
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Commercial | Commercial and Industrial | Accounts receivable
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	12,934
Puerto Rico | Commercial | Commercial and Industrial | Other
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	17,538
Puerto Rico | Leasing
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	1,153,108
Puerto Rico | Consumer | Personal loans
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	1,305,785
Puerto Rico | Consumer | Personal loans | Collateral assets
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	5,480
Puerto Rico | Consumer | Personal loans | Real Estate
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	5,480
Puerto Rico | Consumer | Personal loans | Auto
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Consumer | Personal loans | Equipment
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Consumer | Personal loans | Taxi medallions
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Consumer | Personal loans | Accounts receivable
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Consumer | Personal loans | Other
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Puerto Rico | Consumer | Auto Loan
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	3,045,453
Puerto Rico | Consumer | Other
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	124,052
Popular U.S.
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	7,727,867
Popular U.S. | Collateral assets
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	14,958
Popular U.S. | Real Estate
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	11,351
Popular U.S. | Auto
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Popular U.S. | Equipment
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Popular U.S. | Taxi medallions
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	3,607
Popular U.S. | Accounts receivable
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Popular U.S. | Other
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Popular U.S. | Construction
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	740,209
Popular U.S. | Construction | Collateral assets
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	9,069
Popular U.S. | Construction | Real Estate
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	9,069
Popular U.S. | Construction | Auto
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Popular U.S. | Construction | Equipment
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Popular U.S. | Construction | Taxi medallions
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Popular U.S. | Construction | Accounts receivable
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Popular U.S. | Construction | Other
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Popular U.S. | Mortgages
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	1,097,461
Popular U.S. | Mortgages | Collateral assets
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	527
Popular U.S. | Mortgages | Real Estate
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	527
Popular U.S. | Mortgages | Auto
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Popular U.S. | Mortgages | Equipment
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Popular U.S. | Mortgages | Taxi medallions
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Popular U.S. | Mortgages | Accounts receivable
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Popular U.S. | Mortgages | Other
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Popular U.S. | Commercial | Commercial multi-family
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	1,736,737
Popular U.S. | Commercial | Commercial multi-family | Collateral assets
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	1,755
Popular U.S. | Commercial | Commercial multi-family | Real Estate
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	1,755
Popular U.S. | Commercial | Commercial multi-family | Auto
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Popular U.S. | Commercial | Commercial multi-family | Equipment
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Popular U.S. | Commercial | Commercial multi-family | Taxi medallions
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Popular U.S. | Commercial | Commercial multi-family | Accounts receivable
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Popular U.S. | Commercial | Commercial multi-family | Other
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Popular U.S. | Commercial | CRE non-owner occupied
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	1,939,013
Popular U.S. | Commercial | CRE owner occupied
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	361,126
Popular U.S. | Commercial | Commercial and Industrial
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	1,497,151
Popular U.S. | Commercial | Commercial and Industrial | Collateral assets
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	3,607
Popular U.S. | Commercial | Commercial and Industrial | Real Estate
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Popular U.S. | Commercial | Commercial and Industrial | Auto
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Popular U.S. | Commercial | Commercial and Industrial | Equipment
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Popular U.S. | Commercial | Commercial and Industrial | Taxi medallions
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	3,607
Popular U.S. | Commercial | Commercial and Industrial | Accounts receivable
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Popular U.S. | Commercial | Commercial and Industrial | Other
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	0
Popular U.S. | Consumer | Personal loans
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	233,762
Popular U.S. | Consumer | Other
Accounts, Notes, Loans and Financing Receivable
Notes Receivable Gross	$ 1,300