Loans and the Allowance for Credit Losses - Summary of Changes in Allowance for Credit Losses Disaggregated by Loan Category (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses-loan portfolio, Ending Balance	$ 35,979,000	$ 35,178,000	$ 35,979,000	$ 35,178,000
Provision for (release of) credit losses			(1,107,000)	16,430,000
ASC 326
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses-loan portfolio, Ending Balance	481,000		481,000
Funded Commitments
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses-loan portfolio, Beginning Balance	35,646,000	20,163,000	36,016,000	18,180,000
Provision of acquired loans		8,282,000		8,282,000
Initial allowance for PCD		437,000		437,000
Charge-offs		(158,000)	(3,000)	(448,000)
Recoveries	46,000	23,000	69,000	48,000
Provision for (Release of ) credit losses	(663,000)	5,267,000	(1,053,000)	7,310,000
Allowance for credit losses-loan portfolio, Ending Balance	35,029,000	34,014,000	35,029,000	34,014,000
Funded Commitments | ASC 326
Financing Receivable Allowance For Credit Losses [Line Items]
Adoption of ASC 326				205,000
Unfunded Commitments
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses-loan portfolio, Beginning Balance	1,188,000	283,000	1,004,000	50,000
Provision for (Release of ) credit losses	(238,000)	525,000	(54,000)
Acquired loan commitments				356,000
Provision for (release of) credit losses		356,000		482,000
Allowance for credit losses-unfunded commitments	950,000	1,164,000	950,000	1,164,000
Unfunded Commitments | ASC 326
Financing Receivable Allowance For Credit Losses [Line Items]
Adoption of ASC 326				276,000
Residential Mortgage
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses-loan portfolio, Ending Balance	13,556,000	11,880,000	13,556,000	11,880,000
Residential Mortgage | Funded Commitments
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses-loan portfolio, Beginning Balance	13,144,000	7,477,000	13,067,000	5,141,000
Provision of acquired loans		2,880,000		2,880,000
Initial allowance for PCD		35,000		35,000
Provision for (Release of ) credit losses	412,000	1,488,000	489,000	1,763,000
Allowance for credit losses-loan portfolio, Ending Balance	13,556,000	11,880,000	13,556,000	11,880,000
Residential Mortgage | Funded Commitments | ASC 326
Financing Receivable Allowance For Credit Losses [Line Items]
Adoption of ASC 326				2,061,000
Commercial Mortgage
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses-loan portfolio, Ending Balance	17,301,000	18,067,000	17,301,000	18,067,000
Commercial Mortgage | Funded Commitments
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses-loan portfolio, Beginning Balance	18,693,000	10,881,000	18,564,000	10,905,000
Provision of acquired loans		3,625,000		3,625,000
Initial allowance for PCD		382,000		382,000
Charge-offs		(77,000)		(264,000)
Recoveries	30,000		30,000
Provision for (Release of ) credit losses	(1,422,000)	3,256,000	(1,293,000)	4,866,000
Allowance for credit losses-loan portfolio, Ending Balance	17,301,000	18,067,000	17,301,000	18,067,000
Commercial Mortgage | Funded Commitments | ASC 326
Financing Receivable Allowance For Credit Losses [Line Items]
Adoption of ASC 326				(1,447,000)
Home Equity
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses-loan portfolio, Ending Balance	473,000	652,000	473,000	652,000
Home Equity | Funded Commitments
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses-loan portfolio, Beginning Balance	363,000	310,000	552,000	461,000
Provision of acquired loans		188,000		188,000
Provision for (Release of ) credit losses	110,000	154,000	(79,000)	208,000
Allowance for credit losses-loan portfolio, Ending Balance	473,000	652,000	473,000	652,000
Home Equity | Funded Commitments | ASC 326
Financing Receivable Allowance For Credit Losses [Line Items]
Adoption of ASC 326				(205,000)
Commercial and Industrial
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses-loan portfolio, Ending Balance	3,209,000	2,939,000	3,209,000	2,939,000
Commercial and Industrial | Funded Commitments
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses-loan portfolio, Beginning Balance	2,978,000	946,000	3,309,000	1,475,000
Provision of acquired loans		1,577,000		1,577,000
Initial allowance for PCD		20,000		20,000
Charge-offs		(65,000)		(154,000)
Recoveries	15,000	22,000	34,000	34,000
Provision for (Release of ) credit losses	216,000	439,000	(134,000)	479,000
Allowance for credit losses-loan portfolio, Ending Balance	3,209,000	2,939,000	3,209,000	2,939,000
Commercial and Industrial | Funded Commitments | ASC 326
Financing Receivable Allowance For Credit Losses [Line Items]
Adoption of ASC 326				(492,000)
Consumer
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses-loan portfolio, Ending Balance	490,000	476,000	490,000	476,000
Consumer | Funded Commitments
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses-loan portfolio, Beginning Balance	468,000	549,000	524,000	198,000
Provision of acquired loans		12,000		12,000
Charge-offs		(16,000)	(3,000)	(30,000)
Recoveries	1,000	1,000	5,000	14,000
Provision for (Release of ) credit losses	21,000	(70,000)	(36,000)	(6,000)
Allowance for credit losses-loan portfolio, Ending Balance	490,000	476,000	490,000	476,000
Consumer | Funded Commitments | ASC 326
Financing Receivable Allowance For Credit Losses [Line Items]
Adoption of ASC 326				288,000
Unfunded Commitments
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses-loan portfolio, Ending Balance	950,000	1,164,000	950,000	1,164,000
Unfunded Commitments | Unfunded Commitments
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for credit losses-loan portfolio, Beginning Balance	1,188,000	283,000	1,004,000	50,000
Provision for (Release of ) credit losses	(238,000)	525,000	(54,000)
Acquired loan commitments				356,000
Provision for (release of) credit losses		356,000		482,000
Allowance for credit losses-unfunded commitments	$ 950,000	$ 1,164,000	$ 950,000	1,164,000
Unfunded Commitments | Unfunded Commitments | ASC 326
Financing Receivable Allowance For Credit Losses [Line Items]
Adoption of ASC 326				$ 276,000