Loans and Allowance for Loan Losses - Narrative (Details)	9 Months Ended
	Sep. 30, 2021 USD ($) property loan category	Dec. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)
Financing Receivable, Impaired [Line Items]
Foreclosed properties held	$ 3,400,000
Investment in loans in the process of foreclosure	400,000
Investment in loans in the process of foreclosure, related allowance	$ 0
Number of points in internal risk rating system | category	9
Number of categories in internal risk rating system considered as not criticized | category	6
Commercial relationship credit review threshold amount	$ 1,000,000
Past due period before loans placed in non-accrual status	90 days
Recent loan payment history before removal from non-accrual status	6 months
Allowance for loan losses, number of evaluation components | loan	2
Impaired loans collectively evaluated	$ 1,400,000	$ 2,000,000
Impaired loans, related reserves	$ 100,000	100,000
Number of rolling quarters | loan	12
Liability for unfunded commitments	$ 500,000	$ 500,000
Collectively evaluated for impairment	1,726,961,000		$ 1,373,352,000
Purchased credit impaired loans
Financing Receivable, Impaired [Line Items]
Collectively evaluated for impairment	20,100,000
Residential real estate
Financing Receivable, Impaired [Line Items]
Foreclosed properties held	$ 2,600,000
Increase (decrease) in impaired loans (as a percentage)	76.50%
Number foreclosed properties held | property	11
Collectively evaluated for impairment	$ 262,996,000		231,707,000
Residential real estate | Purchased credit impaired loans
Financing Receivable, Impaired [Line Items]
Collectively evaluated for impairment	4,430,000
Residential real estate | Other Loan Relationships
Financing Receivable, Impaired [Line Items]
Foreclosed properties held	$ 800,000
Increase (decrease) in impaired loans (as a percentage)	23.50%
Commercial and non-residential real estate
Financing Receivable, Impaired [Line Items]
Number foreclosed properties held | property	20
Collectively evaluated for impairment	$ 1,418,142,000		1,102,976,000
Commercial and non-residential real estate | Purchased credit impaired loans
Financing Receivable, Impaired [Line Items]
Collectively evaluated for impairment	$ 15,079,000
Consumer
Financing Receivable, Impaired [Line Items]
Number of additional collateralized loans in the process of foreclosure | loan	5
Investment in loans in the process of foreclosure	$ 200,000
Collectively evaluated for impairment	22,141,000		$ 3,980,000
Consumer | Purchased credit impaired loans
Financing Receivable, Impaired [Line Items]
Collectively evaluated for impairment	601,000
The First State Bank
Financing Receivable, Impaired [Line Items]
Foreclosed properties held	2,700,000
The First State Bank | Consumer
Financing Receivable, Impaired [Line Items]
Investment in loans in the process of foreclosure	$ 200,000