Loans - Nonaccrual Loans and Loans Past Due over 90 Days Still Accruing Interest by Class of Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Past Due [Line Items]
Nonaccrual	$ 21,736	$ 14,262
Past Due Over 90 Days Still on Accrual	61	887
Commercial, industrial, and agricultural
Financing Receivable, Past Due [Line Items]
Nonaccrual	11,644	2,076
Past Due Over 90 Days Still on Accrual	0	487
Commercial mortgages
Financing Receivable, Past Due [Line Items]
Nonaccrual	4,533	6,329
Past Due Over 90 Days Still on Accrual	0	53
Residential real estate
Financing Receivable, Past Due [Line Items]
Nonaccrual	4,724	5,187
Past Due Over 90 Days Still on Accrual	59	299
Consumer
Financing Receivable, Past Due [Line Items]
Nonaccrual	835	670
Past Due Over 90 Days Still on Accrual	0	43
Credit cards
Financing Receivable, Past Due [Line Items]
Nonaccrual	0	0
Past Due Over 90 Days Still on Accrual	$ 2	$ 5