Fair value of financial instruments - Carrying or notional amounts and estimated fair values for financial instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021	Sep. 30, 2021	Dec. 31, 2020
Financial Assets:
Cash and due from banks	$ 2,017,312	$ 428,433
Money market investments	3,975,048	17,536,719
Debt securities available-for-sale	28,264,148	24,968,269
Debt securities held-to-maturity	1,946,500	71,365
Equity securities:
Equity securities, at lower of cost or realizable value	185,923	189,977
Loans held in portfolio	30,820,092	28,545,191
Mortgage servicing rights	130,541	121,570	$ 116,567	$ 118,395
Deposits
Time deposits	6,929,291	6,712,149
Deposits	64,819,327	67,005,088
Assets sold under agreements to repurchase	162,450	91,603
Other short-term borrowings	250,000	75,000
Notes payable:
Notes payable	888,534	988,563
US Treasury Securities
Financial Assets:
Debt securities available-for-sale	21,505,922	15,859,030
Debt securities held-to-maturity	1,881,547
Obligations of Puerto Rico, States and political subdivisions
Financial Assets:
Debt securities held-to-maturity	58,969	65,380
Collateralized Mortgage Obligations - Federal agencies
Financial Assets:
Debt securities available-for-sale	176,204	221,265
Debt securities held-to-maturity	24	25
Securities in wholly owned statutory business trusts
Financial Assets:
Debt securities held-to-maturity	5,960	5,960
Other
Financial Assets:
Debt securities available-for-sale	1,074	128
Carrying amount
Financial Assets:
Cash and due from banks	2,017,312	428,433
Money market investments	3,975,048	17,536,719
Trading account debt securities, excluding derivatives	30,271	29,711
Debt securities available-for-sale	28,264,148	24,968,269
Debt securities held-to-maturity	1,946,500	71,365
Equity securities:
FHLB stock	60,844	59,918
FRB stock	94,870	96,217
Other investments	30,209	33,842
Equity securities, at lower of cost or realizable value	185,923	189,977
Loans held-for-sale	8,065	59,168
Loans held in portfolio	30,820,092	28,545,191
Mortgage servicing rights	130,541	121,570
Derivatives	16,653	26,093
Deposits
Demand deposits	57,890,036	60,292,939
Time deposits	6,929,291	6,712,149
Deposits	64,819,327	67,005,088
Assets sold under agreements to repurchase	162,450	91,603
Other short-term borrowings	250,000	75,000
Notes payable:
FHLB advances	391,429	492,429
Unsecured senior debt securities	298,793	297,842
Junior subordinated deferrable interest debentures (related to trust preferred securities)	198,312	198,292
Notes payable	888,534	988,563
Derivatives	14,776	22,878
Contingent consideration		9,241
Carrying amount | US Treasury Securities
Financial Assets:
Debt securities held-to-maturity	1,881,547
Carrying amount | Obligations of Puerto Rico, States and political subdivisions
Financial Assets:
Debt securities held-to-maturity	58,969	65,380
Carrying amount | Collateralized Mortgage Obligations - Federal agencies
Financial Assets:
Debt securities held-to-maturity	24	25
Carrying amount | Securities in wholly owned statutory business trusts
Financial Assets:
Debt securities held-to-maturity	5,960	5,960
Fair Value
Financial Assets:
Cash and due from banks	2,017,312	428,433
Money market investments	3,975,048	17,536,719
Trading account debt securities, excluding derivatives	30,271	29,711
Debt securities available-for-sale	28,264,148	24,968,269
Debt securities held-to-maturity	1,897,558	83,368
Equity securities:
FHLB stock	60,844	59,918
FRB stock	94,870	96,217
Other investments	31,023	36,210
Equity securities, at lower of cost or realizable value	186,737	192,345
Loans held-for-sale	8,065	59,885
Loans held in portfolio	29,308,370	27,489,583
Mortgage servicing rights	130,541	121,570
Derivatives	16,653	26,093
Deposits
Demand deposits	57,890,036	60,292,939
Time deposits	6,553,096	6,647,301
Deposits	64,443,132	66,940,240
Assets sold under agreements to repurchase	162,380	91,602
Other short-term borrowings	250,000	75,000
Notes payable:
FHLB advances	362,885	496,091
Unsecured senior debt securities	304,080	319,296
Junior subordinated deferrable interest debentures (related to trust preferred securities)	181,574	201,879
Notes payable	848,539	1,017,266
Derivatives	14,776	22,878
Contingent consideration		9,241
Fair Value | US Treasury Securities
Financial Assets:
Debt securities held-to-maturity	1,829,680
Fair Value | Obligations of Puerto Rico, States and political subdivisions
Financial Assets:
Debt securities held-to-maturity	61,894	77,383
Fair Value | Collateralized Mortgage Obligations - Federal agencies
Financial Assets:
Debt securities held-to-maturity	24	25
Fair Value | Securities in wholly owned statutory business trusts
Financial Assets:
Debt securities held-to-maturity	5,960	5,960
Fair Value | Level 1
Financial Assets:
Cash and due from banks	2,017,312	428,433
Money market investments	3,967,849	17,530,640
Trading account debt securities, excluding derivatives	15,711	6,530
Debt securities available-for-sale	5,450,397	0
Debt securities held-to-maturity	0	0
Equity securities:
FHLB stock	0	0
FRB stock	0	0
Other investments	0	0
Equity securities, at lower of cost or realizable value	0	0
Loans held-for-sale	0	0
Loans held in portfolio	0	0
Mortgage servicing rights	0	0
Derivatives	0	0
Deposits
Demand deposits	0	0
Time deposits	0	0
Deposits	0	0
Assets sold under agreements to repurchase	0	0
Other short-term borrowings	0	0
Notes payable:
FHLB advances	0	0
Unsecured senior debt securities	0	0
Junior subordinated deferrable interest debentures (related to trust preferred securities)	0	0
Notes payable	0	0
Derivatives	0	0
Contingent consideration		0
Fair Value | Level 1 | US Treasury Securities
Financial Assets:
Debt securities held-to-maturity	0
Fair Value | Level 1 | Obligations of Puerto Rico, States and political subdivisions
Financial Assets:
Debt securities held-to-maturity	0	0
Fair Value | Level 1 | Collateralized Mortgage Obligations - Federal agencies
Financial Assets:
Debt securities held-to-maturity	0	0
Fair Value | Level 1 | Securities in wholly owned statutory business trusts
Financial Assets:
Debt securities held-to-maturity	0	0
Fair Value | Level 2
Financial Assets:
Cash and due from banks	0	0
Money market investments	7,199	6,079
Trading account debt securities, excluding derivatives	14,170	22,703
Debt securities available-for-sale	22,812,040	24,967,443
Debt securities held-to-maturity	1,835,640	5,960
Equity securities:
FHLB stock	60,844	59,918
FRB stock	94,870	96,217
Other investments	26,723	32,429
Equity securities, at lower of cost or realizable value	182,437	188,564
Loans held-for-sale	0	0
Loans held in portfolio	0	0
Mortgage servicing rights	0	0
Derivatives	16,653	26,093
Deposits
Demand deposits	57,890,036	60,292,939
Time deposits	6,553,096	6,647,301
Deposits	64,443,132	66,940,240
Assets sold under agreements to repurchase	162,380	91,602
Other short-term borrowings	250,000	75,000
Notes payable:
FHLB advances	362,885	496,091
Unsecured senior debt securities	304,080	319,296
Junior subordinated deferrable interest debentures (related to trust preferred securities)	181,574	201,879
Notes payable	848,539	1,017,266
Derivatives	14,776	22,878
Contingent consideration		0
Fair Value | Level 2 | US Treasury Securities
Financial Assets:
Debt securities held-to-maturity	1,829,680
Fair Value | Level 2 | Obligations of Puerto Rico, States and political subdivisions
Financial Assets:
Debt securities held-to-maturity	0	0
Fair Value | Level 2 | Collateralized Mortgage Obligations - Federal agencies
Financial Assets:
Debt securities held-to-maturity	0	0
Fair Value | Level 2 | Securities in wholly owned statutory business trusts
Financial Assets:
Debt securities held-to-maturity	5,960	5,960
Fair Value | Level 3
Financial Assets:
Cash and due from banks	0	0
Money market investments	0	0
Trading account debt securities, excluding derivatives	390	478
Debt securities available-for-sale	1,711	826
Debt securities held-to-maturity	61,918	77,408
Equity securities:
FHLB stock	0	0
FRB stock	0	0
Other investments	3,969	3,704
Equity securities, at lower of cost or realizable value	3,969	3,704
Loans held-for-sale	8,065	59,885
Loans held in portfolio	29,308,370	27,489,583
Mortgage servicing rights	130,541	121,570
Derivatives	0	0
Deposits
Demand deposits	0	0
Time deposits	0	0
Deposits	0	0
Assets sold under agreements to repurchase	0	0
Other short-term borrowings	0	0
Notes payable:
FHLB advances	0	0
Unsecured senior debt securities	0	0
Junior subordinated deferrable interest debentures (related to trust preferred securities)	0	0
Notes payable	0	0
Derivatives	0	0
Contingent consideration		9,241
Fair Value | Level 3 | US Treasury Securities
Financial Assets:
Debt securities held-to-maturity	0
Fair Value | Level 3 | Obligations of Puerto Rico, States and political subdivisions
Financial Assets:
Debt securities held-to-maturity	61,894	77,383
Fair Value | Level 3 | Collateralized Mortgage Obligations - Federal agencies
Financial Assets:
Debt securities held-to-maturity	24	25
Fair Value | Level 3 | Securities in wholly owned statutory business trusts
Financial Assets:
Debt securities held-to-maturity	0	0
Fair Value | NAV
Financial Assets:
Cash and due from banks	0	0
Money market investments	0	0
Trading account debt securities, excluding derivatives	0	0
Debt securities available-for-sale	0	0
Debt securities held-to-maturity	0	0
Equity securities:
FHLB stock	0	0
FRB stock	0	0
Other investments	331	77
Equity securities, at lower of cost or realizable value	331	77
Loans held-for-sale	0	0
Loans held in portfolio	0	0
Mortgage servicing rights	0	0
Derivatives	0	0
Deposits
Demand deposits	0	0
Time deposits	0	0
Deposits	0	0
Assets sold under agreements to repurchase	0	0
Other short-term borrowings	0	0
Notes payable:
FHLB advances	0	0
Unsecured senior debt securities	0	0
Junior subordinated deferrable interest debentures (related to trust preferred securities)	0	0
Notes payable	0	0
Derivatives	0	0
Contingent consideration		0
Fair Value | NAV | US Treasury Securities
Financial Assets:
Debt securities held-to-maturity	0
Fair Value | NAV | Obligations of Puerto Rico, States and political subdivisions
Financial Assets:
Debt securities held-to-maturity	0	0
Fair Value | NAV | Collateralized Mortgage Obligations - Federal agencies
Financial Assets:
Debt securities held-to-maturity	0	0
Fair Value | NAV | Securities in wholly owned statutory business trusts
Financial Assets:
Debt securities held-to-maturity	$ 0	$ 0