Loans - Troubled Debt Restructurings (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Financing Receivable, Troubled Debt Restructuring [Line Items]
Balance at time of restructuring	$ 12,562	$ 8,024
Balance at period end	12,554	7,863
Commercial Portfolio Segment [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Balance at time of restructuring	3,660	677
Balance at period end	3,652	555
Commercial real estate, Buildings, land and other [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Balance at time of restructuring	6,606	7,347
Balance at period end	6,606	7,308
Construction Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Balance at time of restructuring	1,192	0
Balance at period end	1,192	0
Consumer Loan [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Balance at time of restructuring	1,104	0
Balance at period end	$ 1,104	$ 0