Loans and Allowance for Loan Losses - Narrative (Details)	3 Months Ended			6 Months Ended
	Jun. 30, 2020 USD ($) component loan property method	Jun. 30, 2020 USD ($) component loan property method	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) component loan property method	Jun. 30, 2020 USD ($) component loan property method	Jun. 30, 2020 USD ($) component loan property quarter method	Jun. 30, 2020 USD ($) component loan property method	Jun. 30, 2020 USD ($) component loan property method	Jun. 30, 2020 USD ($) component loan property relationship method	Jun. 30, 2020 USD ($) component loan category property method	Jun. 30, 2019 USD ($) relationship loan	Dec. 31, 2019 USD ($)	Jun. 30, 2019 loan	Jun. 30, 2019 property	Jun. 30, 2019 borrower
Financing Receivable, Impaired [Line Items]
Allowance for loan losses, number of evaluation components | component	2	2		2	2	2	2	2	2	2
Impaired loans collectively evaluated	$ 2,100,000	$ 2,100,000		$ 2,100,000	$ 2,100,000	$ 2,100,000	$ 2,100,000	$ 2,100,000	$ 2,100,000	$ 2,100,000		$ 2,000,000.0
Impaired loans, related reserves	69,000	69,000		69,000	69,000	$ 69,000	69,000	69,000	69,000	69,000		139,000
Number of rolling quarters | quarter						12
Liability for unfunded commitments	$ 332,000	$ 332,000		$ 332,000	$ 332,000	$ 332,000	$ 332,000	$ 332,000	$ 332,000	$ 332,000		$ 332,000
Total valuation methods used on impaired loans | method	3	3		3	3	3	3	3	3	3
Increase (decrease) in impaired loans					$ 8,100,000
Increase (decrease) in impaired loans (as a percentage)							85.10%
Impaired loans, identified during the period					8,200,000
Impaired loans, curtailment					348,000
Foreclosure of loan relationship | loan								1
Reclassification to other real estate owned					23,000
Classification to performing loans					26,000
Normal loan amortization					295,000
Collectively evaluated for impairment	$ 1,430,770,000	$ 1,430,770,000	$ 1,315,229,000	$ 1,430,770,000	1,430,770,000	$ 1,430,770,000	$ 1,430,770,000	$ 1,430,770,000	$ 1,430,770,000	$ 1,430,770,000	$ 1,315,229,000
Foreclosed properties held	1,200,000	1,200,000	1,400,000	1,200,000	1,200,000	1,200,000	1,200,000	1,200,000	1,200,000	$ 1,200,000	1,400,000
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	1,000,000		$ 1,000,000	1,000,000	1,000,000	1,000,000	1,000,000	1,000,000	$ 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 reversal		(6,423,000)	(600,000)		(7,561,000)						$ (900,000)
Purchased credit impaired loans
Financing Receivable, Impaired [Line Items]
Collectively evaluated for impairment	48,435,000	48,435,000		$ 48,435,000	48,435,000	48,435,000	48,435,000	48,435,000	48,435,000	48,435,000
Allowance for loan losses reversal		(173,000)			(173,000)
The First State Bank
Financing Receivable, Impaired [Line Items]
Collectively evaluated for impairment	$ 192,000	$ 192,000		$ 192,000	$ 192,000	$ 192,000	$ 192,000	$ 192,000	$ 192,000	$ 192,000
Number foreclosed properties held | loan	81	81		81	81	81	81	81	81	81
Foreclosed properties held	$ 7,700,000	$ 7,700,000		$ 7,700,000	$ 7,700,000	$ 7,700,000	$ 7,700,000	$ 7,700,000	$ 7,700,000	$ 7,700,000
Increase (decrease) in other real estate owned	(4,400,000)
Properties sold	4,400,000
The First State Bank | Purchased credit impaired loans
Financing Receivable, Impaired [Line Items]
Increase in allowance for credit loss		173,000			173,000
Allowance for loan losses reversal		0			0
Commercial and Non-Residential Real Estate
Financing Receivable, Impaired [Line Items]
Increase (decrease) in impaired loans (as a percentage)							74.40%
Impaired loans, identified during the period					6,100,000
Foreclosure of loan relationship								3	1		2
Collectively evaluated for impairment	$ 1,113,420,000	$ 1,113,420,000	977,059,000	$ 1,113,420,000	$ 1,113,420,000	$ 1,113,420,000	$ 1,113,420,000	$ 1,113,420,000	$ 1,113,420,000	$ 1,113,420,000	$ 977,059,000
Foreclosure of unrelated borrower | loan	2	2		2	2	2	2	2	2	2
Allowance for loan losses reversal		$ (5,798,000)	(772,000)		$ (7,053,000)						$ (1,031,000)
Commercial and Non-Residential Real Estate | Purchased credit impaired loans
Financing Receivable, Impaired [Line Items]
Collectively evaluated for impairment	$ 19,799,000	19,799,000		$ 19,799,000	19,799,000	$ 19,799,000	$ 19,799,000	$ 19,799,000	$ 19,799,000	$ 19,799,000
Allowance for loan losses reversal		(121,000)			(121,000)
Commercial, Mortgage, and Home Equity
Financing Receivable, Impaired [Line Items]
Impaired loans, identified during the period					2,100,000
Residential Real Estate
Financing Receivable, Impaired [Line Items]
Increase (decrease) in impaired loans (as a percentage)							30.00%				41.00%
Impaired loans, identified during the period					1,400,000
Foreclosure of loan relationship | loan								4
Collectively evaluated for impairment	$ 276,544,000	$ 276,544,000	270,715,000	$ 276,544,000	$ 276,544,000	$ 276,544,000	$ 276,544,000	$ 276,544,000	$ 276,544,000	$ 276,544,000	$ 270,715,000
Number foreclosed properties held	3	3		3	3	3	3	3	3	3			12	3
Foreclosed properties held	$ 357,000	$ 357,000	583,000	$ 357,000	$ 357,000	$ 357,000	$ 357,000	$ 357,000	$ 357,000	$ 357,000	583,000
Allowance for loan losses reversal		(574,000)	188,000		(574,000)						177,000
Residential Real Estate | Purchased credit impaired loans
Financing Receivable, Impaired [Line Items]
Collectively evaluated for impairment	27,033,000	27,033,000		27,033,000	27,033,000	27,033,000	27,033,000	27,033,000	27,033,000	27,033,000
Allowance for loan losses reversal		(52,000)			(52,000)
Consumer
Financing Receivable, Impaired [Line Items]
Collectively evaluated for impairment	3,525,000	3,525,000	8,812,000	3,525,000	3,525,000	3,525,000	3,525,000	$ 3,525,000	3,525,000	3,525,000	$ 8,812,000
Number of additional collateralized loans in the process of foreclosure | loan								4			2
Investment in loans in the process of foreclosure	214,000	214,000	516,000	214,000	214,000	214,000	214,000	$ 214,000	214,000	214,000	$ 516,000
Investment in loans in the process of foreclosure, related allowance	0	0	0	0	0	0	0	0	0	0	0
Allowance for loan losses reversal		(2,000)	(9,000)		22,000						(20,000)
Consumer | Purchased credit impaired loans
Financing Receivable, Impaired [Line Items]
Collectively evaluated for impairment	$ 1,603,000	1,603,000		$ 1,603,000	1,603,000	$ 1,603,000	$ 1,603,000	$ 1,603,000	$ 1,603,000	$ 1,603,000
Allowance for loan losses reversal		$ 0			0
Home Equity
Financing Receivable, Impaired [Line Items]
Impaired loans, identified during the period					34,000
Commercial Loan Relationship One | Commercial and Non-Residential Real Estate
Financing Receivable, Impaired [Line Items]
Impaired loans, identified during the period					$ 718,000
Foreclosure of loan relationship | loan								2
Number foreclosed properties held | property	2	2		2	2	2	2	2	2	2				2
Commercial Loan Relationship One | Residential Real Estate
Financing Receivable, Impaired [Line Items]
Foreclosed properties held	$ 294,000	$ 294,000	294,000	$ 294,000	$ 294,000	$ 294,000	$ 294,000	$ 294,000	$ 294,000	$ 294,000	294,000
Commercial Loan Relationship Two | Commercial and Non-Residential Real Estate
Financing Receivable, Impaired [Line Items]
Number foreclosed properties held | property														7
Commercial Loan Relationship Two | Residential Real Estate
Financing Receivable, Impaired [Line Items]
Foreclosed properties held			174,000								174,000
Commercial Loan Relationship Three | Residential Real Estate
Financing Receivable, Impaired [Line Items]
Foreclosed properties held	63,000	63,000	115,000	63,000	63,000	63,000	$ 63,000	63,000	63,000	63,000	$ 115,000
Foreclosure of unrelated borrower | borrower															3
Other Loan Relationships | Commercial and Non-Residential Real Estate
Financing Receivable, Impaired [Line Items]
Foreclosure of unrelated borrower | loan													3
Other Loan Relationships | Residential Real Estate
Financing Receivable, Impaired [Line Items]
Increase (decrease) in impaired loans (as a percentage)							70.00%				59.00%
Foreclosed properties held	$ 826,000	$ 826,000	$ 826,000	$ 826,000	$ 826,000	$ 826,000	$ 826,000	$ 826,000	$ 826,000	$ 826,000	$ 826,000