Loans, Allowance for Credit Losses and Credit Quality - Textual (Details) - USD ($)		9 Months Ended
		Sep. 30, 2023		Sep. 30, 2022		Jun. 30, 2023	Dec. 31, 2022	Jun. 30, 2022	Dec. 31, 2021
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for credit losses		$ 140,569,000	[1]	$ 147,313,000	[1]	$ 140,647,000	$ 152,419,000	$ 144,319,000	$ 146,922,000
Unfunded commitments		$ 1,500,000					1,300,000
Days to be termed as non accrual loans		90 days
Additional commitments to lend to borrowers experiencing financial difficulty party to a loan modification		$ 0
Additional commitments to lend to borrowers party to a TDR							64,000
Financing Receivable, Nonaccrual	[2]	39,168,000					54,881,000
Financing Receivable, Troubled Debt Restructuring, Premodification				68,000
Finance Receivable, Troubled Debt Restructurings, Post Modifications [Line Items]
Financing Receivable, Troubled Debt Restructuring, Premodification				68,000
Financing Receivable, Troubled Debt Restructuring, Post Modification [Line Items]				67,000
Financial Asset, Not Past Due | Aging Loan Modification Member
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income		23,801,000
Commercial And Industrial [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for credit losses		16,934,000	[1]	20,169,000	[1]	15,142,000	27,559,000	14,107,000	14,402,000
Financing Receivable, Nonaccrual		2,953,000					26,693,000
Commercial And Industrial [Member] | Financial Asset, Not Past Due | Aging Loan Modification Member
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income		7,409,000
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for credit losses		74,402,000	[1]	$ 80,036,000	[1]	$ 78,396,000	77,799,000	$ 83,456,000	$ 83,486,000
Financing Receivable, Nonaccrual		23,867,000					$ 15,730,000
Commercial Real Estate [Member] | Terms extension and other than insignificant payment delays
Financing Receivable, Allowance for Credit Loss [Line Items]
TDRs modified during the prior twelve months subsequently defaulted		6,700,000
Commercial Real Estate [Member] | Financial Asset, Not Past Due | Aging Loan Modification Member
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and Leases Receivable, Net of Deferred Income		$ 16,252,000

[1] Balances of accrued interest receivable excluded from amortized cost and the calculation of allowance for credit losses amounted to $58.1 million and $42.7 million as of September 30, 2023 and September 30, 2022, respectively.

[2] included $11.5 million of nonaccruing troubled debt restructures ("TDRs"). (2)Nonaccrual balances reported above without an allowance for credit losses are attributable to loans evaluated on an individual basis where it was determined that there was no risk of loss due to sufficient underlying collateral values.