Loans Held for Investment and Allowance for Loan Losses - Schedule of How Loans Were Modified as Troubled Debt Restructured Loans (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($)
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	$ 846
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	149
Commercial [Member] | C&I [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	149
Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	697
Real Estate [Member] | Owner Occupied CRE [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	500
Real Estate [Member] | Residential [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	197
Combined Rate and Maturity [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	846
Combined Rate and Maturity [Member] | Commercial [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	149
Combined Rate and Maturity [Member] | Commercial [Member] | C&I [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	149
Combined Rate and Maturity [Member] | Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	697
Combined Rate and Maturity [Member] | Real Estate [Member] | Owner Occupied CRE [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	500
Combined Rate and Maturity [Member] | Real Estate [Member] | Residential [Member]
Financing Receivable, Modifications [Line Items]
Troubled Debt Restructured Loans	$ 197