Loans - Additional Information (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) loan	Jun. 30, 2018 USD ($) loan	Dec. 31, 2018 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net unamortized loan fees	$ 3,374,000		$ 3,374,000		$ 3,175,000
Percentage of comprised loan, commercial, industrial and agricultural loans	38.00%		38.00%		37.00%
Percentage of comprised loan, commercial mortgage loans	29.00%		29.00%		28.00%
Percentage of loan-to-value to business equipment			80.00%
Percentage of loan-to-value to accounts receivable			75.00%
Percentage of loan-to-value to business inventory			60.00%
Percentage of loan-to-value to real estate			85.00%
Percentage of residential real estate loan in portfolio	30.00%		30.00%		31.00%
Minimum period to be considered for loan to have defaulted			90 days
Loans modified as troubled debt restructuring with subsequent defaults | loan			0	0
Principal balances forgiven in connection with loan restructuring	$ 0		$ 0		$ 0
Number of loans, period of time | loan			0	4
Modified in a troubled debt restructuring	12,872,000		$ 12,872,000		$ 14,626,000
Financing receivable, allowance for credit losses, w-downs	$ 773,000	$ 710,000	$ 1,576,000	$ 1,436,000
Maximum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Maximum percentage of consumer loan and credit card in portfolio	4.00%		4.00%		4.00%