Revenue from Contracts with Customers - Additional Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($) Contract	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) Contract Fee RevenueCategory	Sep. 30, 2017 USD ($)
Revenue From Contract With Customer [Line Items]
Number of types of interchange fees | Fee			2
Other real estate sales, net gains | $	$ 224	$ 200	$ 1,226	$ 1,722
Number of trust management revenue categories | RevenueCategory			5
Time period between service obligation completed and payment received from trust customer			30 days
Number of general categories of insurance contracts | Contract	4		4
Commercial Installment Insurance Contracts [Member]
Revenue From Contract With Customer [Line Items]
Revenue recognition contract term	1 year		1 year
Personal Insurance Contracts [Member]
Revenue From Contract With Customer [Line Items]
Revenue recognition contract term	1 year		1 year
Employee Benefits Insurance Contracts [Member]
Revenue From Contract With Customer [Line Items]
Revenue recognition contract term	1 year		1 year
Contingency Commission Insurance Contracts [Member]
Revenue From Contract With Customer [Line Items]
Revenue recognition contract term	1 year		1 year
Maximum [Member] | Insurance Contracts [Member]
Revenue From Contract With Customer [Line Items]
Revenue recognition contract term	1 year		1 year
Maximum [Member] | Personal Insurance Contracts [Member]
Revenue From Contract With Customer [Line Items]
Insurance contracts payment received period			60 days
Maximum [Member] | Employee Benefits Insurance Contracts [Member]
Revenue From Contract With Customer [Line Items]
Insurance contracts payment received period			90 days
Minimum [Member] | Personal Insurance Contracts [Member]
Revenue From Contract With Customer [Line Items]
Insurance contracts payment received period			30 days
Minimum [Member] | Employee Benefits Insurance Contracts [Member]
Revenue From Contract With Customer [Line Items]
Insurance contracts payment received period			60 days