Commitments and Contingent Liabilities - Additional Information (Details)	12 Months Ended
	Dec. 31, 2018 USD ($) Facility Contract	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Banking Facility Leases [Abstract]
Number of banking facility leases | Facility	3
Rent expense	$ 686,000	$ 679,000	$ 676,000
Data Processing Contractual Obligations [Abstract]
Number of data processing contractual obligations greater than one year | Contract	2
Data processing	$ 1,292,000	1,254,000	1,264,000
Cash Segregated under Federal Regulations [Abstract]
Daily average required cash balances with the Federal Reserve Bank	0	23,800,000
Core Data Processing [Member]
Data Processing Contractual Obligations [Abstract]
Data processing	1,200,000	1,100,000	1,100,000
Interchange Processing [Member]
Data Processing Contractual Obligations [Abstract]
Interchange expense	$ 890,000	$ 739,000	$ 831,000