Mergers and Acquisitions - United American Savings Bank, Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Apr. 30, 2016	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Goodwill		$ 10,288	$ 10,288
Intangible asset amortization		246	226
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
2018		236
2019		55
2020		43
2021		33
2022		29
Thereafter		85
Acquisition costs		1,119	401
United American Savings Bank
Business Acquisition [Line Items]
Payments to acquire businesses, gross	$ 13,200
Acquisition share price (in dollars per share)	$ 42.67
Goodwill	$ 6,624		6,600
Core deposit intangible	232
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
Loans receivable	66,145
Credit related adjustment	927
Adjustment for other factors	$ 982
Acquisition costs			401
Legal fees			194
Conversion costs			132
Other costs			$ 75
United American Savings Bank | Core Deposits
Business Acquisition [Line Items]
Weighted average useful life	10 years
Intangible asset amortization		40
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
2018		32
2019		26
2020		21
2021		17
2022		15
Thereafter		$ 52