Commitments (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Unadvanced Commitment on Impaired Loan
Schedule of Commitments [Line Items]
Estimated losses attributable to unadvanced commitments on impaired loans	$ 9,800	$ 12,100
Commitments to extend credit
Schedule of Commitments [Line Items]
Off-balance sheet financial instruments, contractual amounts	3,134,567	3,113,966
Commitments to extend credit | Fixed Rate Loan Commitment
Schedule of Commitments [Line Items]
Off-balance sheet financial instruments, contractual amounts	219,700	246,500
Letters of credit
Schedule of Commitments [Line Items]
Off-balance sheet financial instruments, contractual amounts	$ 105,652	$ 68,544
Letters of credit | Maximum
Schedule of Commitments [Line Items]
Remaining term	10 years
Letters of credit | Minimum
Schedule of Commitments [Line Items]
Remaining term	1 month