Mergers and Acquisitions - Northern Hancock Bank & Trust Co., Additional Information (Details) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Gain on bargain purchase			$ 1,316	$ 0
Intangible asset amortization			246	226
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
2018		$ 236	236
2019		55	55
2020		43	43
2021		33	33
2022		29	29
Thereafter		85	85
Acquisition costs			1,119	$ 401
Northern Hancock
Business Acquisition [Line Items]
Equity interest issued (in shares)	54,445
Common stock	$ 1,674
Payments to acquire businesses, gross	22
Gain on bargain purchase	1,316
Core deposit intangible	167
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
Acquired receivables	18,500
Credit related adjustment	(566)
Adjustment for other factors	537
Acquisition costs			1,100
Conversion costs			421
Contract termination fees			279
Legal fees			173
Severance costs			108
Accounting and auditing costs			55
Other costs			84
Core Deposits | Northern Hancock
Business Acquisition [Line Items]
Core deposit intangible	$ 167
Weighted average useful life	8 years
Intangible asset amortization		11
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
2018		40	40
2019		30	30
2020		22	22
2021		17	17
2022		13	13
Thereafter		$ 34	$ 34