Loans - Amortized cost basis and interest income recognized on non-accrual loans (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Financing receivable nonaccrual status
Non-accrual with no allowance	$ 261,918	$ 203,460
Non-accrual with allowance	370,917	534,314
Construction
Financing receivable nonaccrual status
Non-accrual with no allowance	14,877	0
Non-accrual with allowance	0	29,057
Mortgages
Financing receivable nonaccrual status
Non-accrual with no allowance	179,928	142,254
Non-accrual with allowance	189,115	286,953
Commercial | Commercial multi-family
Financing receivable nonaccrual status
Non-accrual with no allowance	0	0
Non-accrual with allowance	396	2,399
Commercial | CRE non-owner occupied
Financing receivable nonaccrual status
Non-accrual with no allowance	28,883	35,968
Non-accrual with allowance	31,634	41,838
Commercial | CRE owner occupied
Financing receivable nonaccrual status
Non-accrual with no allowance	14,358	14,825
Non-accrual with allowance	58,491	77,510
Commercial | Commercial and Industrial
Financing receivable nonaccrual status
Non-accrual with no allowance	15,423	1,148
Non-accrual with allowance	36,996	36,392
Leasing
Financing receivable nonaccrual status
Non-accrual with no allowance	166	0
Non-accrual with allowance	2,376	3,441
Consumer | Home equity lines of credit
Financing receivable nonaccrual status
Non-accrual with no allowance	0	0
Non-accrual with allowance	5,941	7,491
Consumer | Personal loans
Financing receivable nonaccrual status
Non-accrual with no allowance	7,516	9,265
Non-accrual with allowance	14,878	18,596
Consumer | Auto Loan
Financing receivable nonaccrual status
Non-accrual with no allowance	767	0
Non-accrual with allowance	16,578	15,736
Consumer | Other
Financing receivable nonaccrual status
Non-accrual with no allowance	0	0
Non-accrual with allowance	14,512	14,901
Puerto Rico
Financing receivable nonaccrual status
Non-accrual with no allowance	261,885	202,943
Non-accrual with allowance	346,986	497,434
Puerto Rico | Construction
Financing receivable nonaccrual status
Non-accrual with no allowance	14,877	0
Non-accrual with allowance	0	21,497
Puerto Rico | Mortgages
Financing receivable nonaccrual status
Non-accrual with no allowance	179,895	141,737
Non-accrual with allowance	174,660	272,606
Puerto Rico | Commercial | Commercial multi-family
Financing receivable nonaccrual status
Non-accrual with no allowance	0	0
Non-accrual with allowance	396	505
Puerto Rico | Commercial | CRE non-owner occupied
Financing receivable nonaccrual status
Non-accrual with no allowance	28,883	35,968
Non-accrual with allowance	31,260	41,169
Puerto Rico | Commercial | CRE owner occupied
Financing receivable nonaccrual status
Non-accrual with no allowance	14,358	14,825
Non-accrual with allowance	57,505	77,176
Puerto Rico | Commercial | Commercial and Industrial
Financing receivable nonaccrual status
Non-accrual with no allowance	15,423	1,148
Non-accrual with allowance	35,569	33,301
Puerto Rico | Leasing
Financing receivable nonaccrual status
Non-accrual with no allowance	166	0
Non-accrual with allowance	2,376	3,441
Puerto Rico | Consumer | Home equity lines of credit
Financing receivable nonaccrual status
Non-accrual with no allowance	0	0
Non-accrual with allowance	0	0
Puerto Rico | Consumer | Personal loans
Financing receivable nonaccrual status
Non-accrual with no allowance	7,516	9,265
Non-accrual with allowance	14,130	17,122
Puerto Rico | Consumer | Auto Loan
Financing receivable nonaccrual status
Non-accrual with no allowance	767	0
Non-accrual with allowance	16,578	15,736
Puerto Rico | Consumer | Other
Financing receivable nonaccrual status
Non-accrual with no allowance	0	0
Non-accrual with allowance	14,512	14,881
Popular U.S.
Financing receivable nonaccrual status
Non-accrual with no allowance	33	517
Non-accrual with allowance	23,931	36,880
Popular U.S. | Construction
Financing receivable nonaccrual status
Non-accrual with no allowance	0	0
Non-accrual with allowance	0	7,560
Popular U.S. | Mortgages
Financing receivable nonaccrual status
Non-accrual with no allowance	33	517
Non-accrual with allowance	14,455	14,347
Popular U.S. | Commercial | Commercial multi-family
Financing receivable nonaccrual status
Non-accrual with no allowance	0	0
Non-accrual with allowance	0	1,894
Popular U.S. | Commercial | CRE non-owner occupied
Financing receivable nonaccrual status
Non-accrual with no allowance	0	0
Non-accrual with allowance	374	669
Popular U.S. | Commercial | CRE owner occupied
Financing receivable nonaccrual status
Non-accrual with no allowance	0	0
Non-accrual with allowance	986	334
Popular U.S. | Commercial | Commercial and Industrial
Financing receivable nonaccrual status
Non-accrual with no allowance	0	0
Non-accrual with allowance	1,427	3,091
Popular U.S. | Leasing
Financing receivable nonaccrual status
Non-accrual with no allowance	0	0
Non-accrual with allowance	0	0
Popular U.S. | Consumer | Home equity lines of credit
Financing receivable nonaccrual status
Non-accrual with no allowance	0	0
Non-accrual with allowance	5,941	7,491
Popular U.S. | Consumer | Personal loans
Financing receivable nonaccrual status
Non-accrual with no allowance	0	0
Non-accrual with allowance	748	1,474
Popular U.S. | Consumer | Auto Loan
Financing receivable nonaccrual status
Non-accrual with no allowance	0	0
Non-accrual with allowance	0	0
Popular U.S. | Consumer | Other
Financing receivable nonaccrual status
Non-accrual with no allowance	0	0
Non-accrual with allowance	$ 0	$ 20