Allowance for Loan and Lease Losses and Reserve for Unfunded Commitments - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Loans And Leases Receivable Disclosure [Line Items]
Increase (decrease) in allowance for loan and lease losses	$ 10,000,000.0	$ 453,000	$ 29,300,000	$ 6,400,000
Commitments outstanding on troubled debt restructurings	0		0		$ 500,000
Recorded investment in troubled debt restructurings that subsequently defaulted within twelve months	0	0	0	348,000
Reserve for unfunded commitments	2,400,000		2,400,000		$ 1,200,000
Provisions for (credits to) unfunded commitments	519,000	51,000	1,200,000	78,000
Charge-offs or recoveries related to reserve for unfunded commitments	0	0	$ 0	0
Paycheck Protection Program ("PPP")
Loans And Leases Receivable Disclosure [Line Items]
Percentage of guarantee on SBA			100.00%
Acquired Impaired Loans
Loans And Leases Receivable Disclosure [Line Items]
Increase (decrease) in allowance for loan and lease losses	295,000	(480,000)	$ 2,300,000	260,000
Individually Evaluated For Impairment
Loans And Leases Receivable Disclosure [Line Items]
Increase (decrease) in allowance for loan and lease losses	768,000	276,000	4,100,000	2,900,000
Collectively Evaluated For Impairment
Loans And Leases Receivable Disclosure [Line Items]
Increase (decrease) in allowance for loan and lease losses	$ 8,900,000	$ 850,000	$ 23,000,000.0	$ 3,400,000