Loans and Allowance for Credit Losses - Recorded Investment, Principal Balance and Related Allowance (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment					$ 58,144,000
Unpaid principal balances					64,556,000
Valuation allowance	$ 10,700,000		$ 10,700,000		3,280,000
Impaired Financing Receivable, Average Recorded Investment		$ 73,649,000		$ 81,612,000
Impaired Financing Receivable, Interest Income, Cash Basis Method	0	0	0	176,000
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans	910,000	1,300,000	2,100,000	3,500,000
Currently performing impaired loans	$ 40,700,000		$ 40,700,000		35,800,000
Impaired loans with an allowance:
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment					35,758,000
Unpaid principal balances					40,305,000
Valuation allowance					3,280,000
Impaired Financing Receivable, Average Recorded Investment		44,265,000		46,633,000
Impaired Financing Receivable, Interest Income, Cash Basis Method		0		0
Impaired loans with an allowance: | Commercial real estate – mortgage
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment					9,998,000
Unpaid principal balances					10,983,000
Valuation allowance					1,235,000
Impaired Financing Receivable, Average Recorded Investment		13,050,000		14,689,000
Impaired Financing Receivable, Interest Income, Cash Basis Method		0		0
Impaired loans with an allowance: | Consumer real estate – mortgage
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment					20,996,000
Unpaid principal balances					23,105,000
Valuation allowance					1,292,000
Impaired Financing Receivable, Average Recorded Investment		19,508,000		20,887,000
Impaired Financing Receivable, Interest Income, Cash Basis Method		0		0
Impaired loans with an allowance: | Construction and land development
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment					542,000
Unpaid principal balances					654,000
Valuation allowance					33,000
Impaired Financing Receivable, Average Recorded Investment		451,000		587,000
Impaired Financing Receivable, Interest Income, Cash Basis Method		0		0
Impaired loans with an allowance: | Commercial and industrial
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment					4,074,000
Unpaid principal balances					5,381,000
Valuation allowance					711,000
Impaired Financing Receivable, Average Recorded Investment		11,113,000		10,070,000
Impaired Financing Receivable, Interest Income, Cash Basis Method		0		0
Impaired loans with an allowance: | Consumer and other
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment					148,000
Unpaid principal balances					182,000
Valuation allowance					9,000
Impaired Financing Receivable, Average Recorded Investment		143,000		400,000
Impaired Financing Receivable, Interest Income, Cash Basis Method		0		0
Impaired loans without an allowance:
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment					22,386,000
Unpaid principal balances					24,251,000
Valuation allowance					0
Impaired Financing Receivable, Average Recorded Investment		29,384,000		34,979,000
Impaired Financing Receivable, Interest Income, Cash Basis Method		0		176,000
Impaired loans without an allowance: | Commercial real estate – mortgage
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment					8,124,000
Unpaid principal balances					8,891,000
Valuation allowance					0
Impaired Financing Receivable, Average Recorded Investment		9,344,000		12,521,000
Impaired Financing Receivable, Interest Income, Cash Basis Method		0		176,000
Impaired loans without an allowance: | Consumer real estate – mortgage
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment					4,022,000
Unpaid principal balances					4,021,000
Valuation allowance					0
Impaired Financing Receivable, Average Recorded Investment		7,922,000		8,381,000
Impaired Financing Receivable, Interest Income, Cash Basis Method		0		0
Impaired loans without an allowance: | Construction and land development
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment					19,000
Unpaid principal balances					17,000
Valuation allowance					0
Impaired Financing Receivable, Average Recorded Investment		10,000		452,000
Impaired Financing Receivable, Interest Income, Cash Basis Method		0		0
Impaired loans without an allowance: | Commercial and industrial
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment					10,221,000
Unpaid principal balances					11,322,000
Valuation allowance					0
Impaired Financing Receivable, Average Recorded Investment		12,108,000		13,625,000
Impaired Financing Receivable, Interest Income, Cash Basis Method		0		0
Impaired loans without an allowance: | Consumer and other
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Recorded Investment					0
Unpaid principal balances					0
Valuation allowance					$ 0
Impaired Financing Receivable, Average Recorded Investment		0		0
Impaired Financing Receivable, Interest Income, Cash Basis Method		$ 0		$ 0