Loans and Allowance for Loan Losses - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable Recorded Investment Past Due [Line Items]
Carrying value of PCI loans	$ 88,835,000	$ 16,058,000	$ 21,375,000
Non-accrual loans	3,205,000	4,265,000
Accretion of interest income	5,419,000	3,538,000	493,000
Recorded investment in troubled debt restructurings	8,604,000	8,802,000
Allocation to specific reserves	172,000	402,000
Commitments to lend additional amounts to customers	2,000	1,000
Payment default for loans modified as troubled debt restructurings	0	0
Purchased Credit Impaired
Financing Receivable Recorded Investment Past Due [Line Items]
Carrying value of PCI loans	88,835,000	16,058,000
Non-accrual loans	0	0
Accretion of interest income	5,299,000	2,631,000	454,000
Total purchase accounting contribution through accretion for purchased loans	5,419,000	3,538,000	$ 493,000
Federal Reserve | Borrower in Custody Program
Financing Receivable Recorded Investment Past Due [Line Items]
Gross loans	724,312,000	1,072,118,000
Federal Home Loan Bank of Cincinnati
Financing Receivable Recorded Investment Past Due [Line Items]
Gross loans	$ 968,567,000	$ 565,717,000