Description of Business and Summary of Significant Accounting Policies - Schedule of Portfolio Segments Weighted Average Life, and Measures the Allowance for Credit Losses (Detail) - ASC 326 [Member]	12 Months Ended
	Dec. 31, 2020
Real Estate [Member] | Commercial Real Estate Owner Occupied [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Loan Segment, Life (in years)	9 years
Real Estate [Member] | Commercial Real Estate Non-Owner Occupied [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Loan Segment, Life (in years)	6 years
Real Estate [Member] | Construction and Development Less than 60 Months [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Loan Segment, Life (in years)	3 years
Real Estate [Member] | Construction Residential Real Estate Less than 60 Months [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Loan Segment, Life (in years)	1 year
Real Estate [Member] | Residential Real Estate First Lien [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Loan Segment, Life (in years)	13 years
Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Loan Segment, Life (in years)	6 years
Real Estate [Member] | Farmland [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Loan Segment, Life (in years)	12 years
Commercial and Agricultural Non-Real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Loan Segment, Life (in years)	3 years
Consumer Non-real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Loan Segment, Life (in years)	4 years
Oil and Gas [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Loan Segment, Life (in years)	1 year
Other Loans [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Loan Segment, Life (in years)	8 years
Pegasus Bank [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Loan Segment, Life (in years)	4 years