Allowance for credit losses - loans held-in-portfolio - Schedule of Amortized Cost Basis of Modified Financing Receivables That Subsequently Defaulted (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	$ 87,852	$ 8,138	$ 94,337	$ 12,697
Mortgage
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	4,572	5,734	10,413	9,540
Commercial | CRE Non-owner occupied
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	99	448	99	448
Commercial | CRE Owner occupied
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	162	254	162	517
Commercial | Commercial and industrial
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	81,671	388	81,754	524
Consumer | Credit cards
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	1,071	943	1,455	1,273
Consumer | Personal
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	277	371	454	395
Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	205	369	233	532
Interest Rate Reduction | Mortgage
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	0	0	0	0
Interest Rate Reduction | Commercial | CRE Non-owner occupied
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	0	0	0	0
Interest Rate Reduction | Commercial | CRE Owner occupied
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	0	0	0	0
Interest Rate Reduction | Commercial | Commercial and industrial
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	14	70	14	99
Interest Rate Reduction | Consumer | Credit cards
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	120	172	121	290
Interest Rate Reduction | Consumer | Personal
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	71	127	98	143
Term Extension
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	4,432	4,583	9,564	8,322
Term Extension | Mortgage
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	4,386	4,478	9,513	8,129
Term Extension | Commercial | CRE Non-owner occupied
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	0	0	0	0
Term Extension | Commercial | CRE Owner occupied
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	0	0	0	88
Term Extension | Commercial | Commercial and industrial
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	46	0	51	0
Term Extension | Consumer | Credit cards
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	0	0	0	0
Term Extension | Consumer | Personal
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	0	105	0	105
Other-Than-Insignificant Payment Delays
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	81,629	702	81,738	907
Other-Than-Insignificant Payment Delays | Mortgage
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	0	0	109	0
Other-Than-Insignificant Payment Delays | Commercial | CRE Non-owner occupied
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	99	448	99	448
Other-Than-Insignificant Payment Delays | Commercial | CRE Owner occupied
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	162	254	162	429
Other-Than-Insignificant Payment Delays | Commercial | Commercial and industrial
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	81,368	0	81,368	30
Other-Than-Insignificant Payment Delays | Consumer | Credit cards
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	0	0	0	0
Other-Than-Insignificant Payment Delays | Consumer | Personal
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	0	0	0	0
Combination - Term Extension and Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	487	1,395	1,242	1,558
Combination - Term Extension and Interest Rate Reduction | Mortgage
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	186	1,256	791	1,411
Combination - Term Extension and Interest Rate Reduction | Commercial | CRE Non-owner occupied
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	0	0	0	0
Combination - Term Extension and Interest Rate Reduction | Commercial | CRE Owner occupied
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	0	0	0	0
Combination - Term Extension and Interest Rate Reduction | Commercial | Commercial and industrial
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	95	0	95	0
Combination - Term Extension and Interest Rate Reduction | Consumer | Credit cards
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	0	0	0	0
Combination - Term Extension and Interest Rate Reduction | Consumer | Personal
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	206	139	356	147
Combination - Other- Than-Insignificant Payment Delays and Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	1,099	1,089	1,560	1,378
Combination - Other- Than-Insignificant Payment Delays and Interest Rate Reduction | Mortgage
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	0	0	0	0
Combination - Other- Than-Insignificant Payment Delays and Interest Rate Reduction | Commercial | CRE Non-owner occupied
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	0	0	0	0
Combination - Other- Than-Insignificant Payment Delays and Interest Rate Reduction | Commercial | CRE Owner occupied
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	0	0	0	0
Combination - Other- Than-Insignificant Payment Delays and Interest Rate Reduction | Commercial | Commercial and industrial
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	148	318	226	395
Combination - Other- Than-Insignificant Payment Delays and Interest Rate Reduction | Consumer | Credit cards
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	951	771	1,334	983
Combination - Other- Than-Insignificant Payment Delays and Interest Rate Reduction | Consumer | Personal
Financing Receivable, Modified [Line Items]
Financing receivable modifications that defaulted	$ 0	$ 0	$ 0	$ 0