Mortgage Loan Servicing, Origination, and Loans Held for Sale (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Mortgage Loan Servicing, Origination, and Loans Held for Sale
Residential mortgages serviced for others	$ 6,600,000		$ 6,600,000		$ 6,600,000
Contractually specified servicing fees earned	$ 4,100	$ 4,200	$ 12,400	$ 12,100
Contractually Specified Servicing Fee Income, Statement of Income or Comprehensive Income [Extensible Enumeration]	Revenue from Contract with Customer, Excluding Assessed Tax	Revenue from Contract with Customer, Excluding Assessed Tax	Revenue from Contract with Customer, Excluding Assessed Tax	Revenue from Contract with Customer, Excluding Assessed Tax
Mortgage servicing rights	$ 89,476		$ 89,476		$ 86,610
Changes in the fair value of MSRs and its offsetting hedge.
(Decrease) increase in fair value of MSRs	1,762	$ 2,661	2,450	$ 18,274
Decay of MSRs	(2,543)	(2,530)	(6,336)	(8,052)
Gain (loss) related to derivatives	(2,170)	(3,572)	(4,288)	(17,963)
Net effect on Consolidated Statements of Net Income	$ (2,951)	$ (3,441)	$ (8,174)	$ (7,741)
Characteristics and sensitivity analysis of the MSR
Composition of residential loans serviced for others	100.00%		100.00%		100.00%
Weighted average life (in years)			8 years 3 months 3 days		8 years 4 months 13 days
Constant Prepayment rate (CPR) (as a percent)			6.60%		6.40%
Weighted average discount rate (as a percent)			10.60%		10.00%
Effect on fair value due to change in interest rates:
25 basis point increase	$ 686		$ 686		$ 774
50 basis point increase	1,231		1,231		1,428
25 basis point decrease	(848)		(848)		(902)
50 basis point decrease	$ (1,877)		$ (1,877)		$ (1,938)
Fixed-rate mortgage loans
Characteristics and sensitivity analysis of the MSR
Composition of residential loans serviced for others	100.00%		100.00%		100.00%