Goodwill and Intangible Assets - Additional Information (Details)	12 Months Ended
	Dec. 31, 2017 USD ($) acquisition	Dec. 31, 2016 USD ($)	Apr. 30, 2016 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
Number of acquisitions resulting in goodwill | acquisition	4
Business Acquisition [Line Items]
Goodwill	$ 10,288,000	$ 10,288,000
Goodwill impairment loss	$ 0	0
Number of acquisitions resulting in intangible assets | acquisition	3
Intangible asset amortization	$ 246,000	226,000
United American Savings Bank
Business Acquisition [Line Items]
Goodwill		$ 6,600,000	$ 6,624,000