Premises and Equipment - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) contract director	Dec. 31, 2017 USD ($) director	Dec. 31, 2016 USD ($) director
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 5.0	$ 5.1	$ 5.0
Lease expiration year	Jan. 01, 2054
Capital lease obligations, number of contracts | contract	2
Rental expense	$ 3.9	$ 4.0	$ 4.1
Number of directors | director	1	1	1
Directors
Property, Plant and Equipment [Line Items]
Rental expense for premises leases with two directors	$ 0.2	$ 0.2	$ 0.3