Loans - Troubled Debt Restructurings (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Financing Receivable, Troubled Debt Restructuring [Line Items]
Balance at time of restructuring	$ 2,191	$ 6,208
Balance at period end	2,198	6,191
Commercial Portfolio Segment [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Balance at time of restructuring	2,191	307
Balance at period end	2,198	293
Commercial real estate, Buildings, land and other [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Balance at time of restructuring	0	5,901
Balance at period end	$ 0	$ 5,898