Loans - Additional Information (Details)	12 Months Ended
	Dec. 31, 2020 USD ($) contract	Dec. 31, 2019 USD ($) contract	Dec. 31, 2018 USD ($) contract	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)
Financing Receivable, Troubled Debt Restructuring [Line Items]
Net deferred costs		$ 19,900,000
Remaining fair value adjustment for loans acquired	$ 30,200,000	$ 34,900,000
Percentage of fair value adjustment for loans acquired	2.86%	3.80%
Accrued interest receivable	$ 25,800,000	$ 14,900,000
Interest income on nonaccrual loans	900,000	1,300,000	$ 400,000
Loans to directors and executive officers	1,100,000	1,700,000
New loans offered	0
Value of loans deferred, not classified as TDRs	$ 74,062,000			$ 702,650,000	$ 1,077,043,000
Percentage on payment deferral	1.00%				21.00%
Allowance for credit loss on TDRs	$ 200,000	$ 0	$ 500,000
Number of loans under trouble debt restructuring | contract	0	4	0
Value of loans under trouble debt restructuring modified in preceding twelve months		$ 3,200,000
Interest income related to impaired loans with impairment measured on present value of expected future cash flows	$ 100,000	$ 100,000	$ 200,000
Portfolio Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Net deferred costs	22,600,000
Portfolio Loans | Paycheck Protection Program
Financing Receivable, Troubled Debt Restructuring [Line Items]
Net deferred fees	$ 9,500,000