Loans, Allowance for Credit Losses and Credit Quality - Financing Receivable, Allowance for Credit Loss (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2023	Mar. 31, 2022
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		$ 152,419	$ 146,922
Charge-offs		(815)	(706)
Recoveries		277	302
Provision for (release of) credit losses		7,250	(2,000)
Ending balance	[1]	159,131	144,518
Commercial And Industrial [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		27,559	14,402
Charge-offs		(281)	0
Recoveries		5	13
Provision for (release of) credit losses		9,649	(246)
Ending balance	[1]	36,932	14,169
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		77,799	83,486
Charge-offs		0	0
Recoveries		0	3
Provision for (release of) credit losses		(1,601)	947
Ending balance	[1]	76,198	84,436
Construction Loans [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		10,762	12,316
Charge-offs		0	0
Recoveries		0	0
Provision for (release of) credit losses		(1,514)	(449)
Ending balance	[1]	9,248	11,867
Small Business [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		2,834	3,508
Charge-offs		(28)	(48)
Recoveries		31	26
Provision for (release of) credit losses		501	(327)
Ending balance	[1]	3,338	3,159
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		20,973	14,484
Charge-offs		0	0
Recoveries		0	0
Provision for (release of) credit losses		(519)	3,904
Ending balance	[1]	20,454	18,388
Home Equity Loan [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		11,504	17,986
Charge-offs		0	(24)
Recoveries		16	26
Provision for (release of) credit losses		908	(6,238)
Ending balance	[1]	12,428	11,750
Consumer - Other [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		988	740
Charge-offs		(506)	(634)
Recoveries		225	234
Provision for (release of) credit losses		(174)	409
Ending balance	[1]	$ 533	$ 749

[1] Balances of accrued interest receivable excluded from amortized cost and the calculation of allowance for credit losses amounted to $52.7 million and $39.4 million as of March 31, 2023 and March 31, 2022, respectively.