Commitments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Unadvanced Commitment on Impaired Loan
Schedule of Commitments [Line Items]
Estimated losses attributable to unadvanced commitments on impaired loans	$ 8,400	$ 7,600
Commitments to extend credit
Schedule of Commitments [Line Items]
Off-balance sheet financial instruments, contractual amounts	2,710,183	2,481,173
Commitments to extend credit | Fixed Rate Loan Commitment
Schedule of Commitments [Line Items]
Off-balance sheet financial instruments, contractual amounts	244,200	238,700
Letters of credit
Schedule of Commitments [Line Items]
Off-balance sheet financial instruments, contractual amounts	$ 78,568	$ 77,314
Letters of credit | Maximum
Schedule of Commitments [Line Items]
Remaining term	11 years
Letters of credit | Minimum
Schedule of Commitments [Line Items]
Remaining term	1 month