Fair Value of Financial Instruments - Included in Notes Payable are the FHLB loan and Subordinated Debentures (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Document Period End Date	Sep. 30, 2018
Federal Home Loan Bank Advances [Member]
Debt Instrument [Line Items]
Interest rate (percent)	1.73%	1.73%
FHLB loan due and issued with fixed interest, Senior notes due and issued with fixed interest and Affiliate subordinated debentures due with variable interest	$ 21,500,000
Federal Home Loan Bank of Cincinnati [Member]
Debt Instrument [Line Items]
Interest rate (percent)	0.00%	5.03%
FHLB loan due and issued with fixed interest, Senior notes due and issued with fixed interest and Affiliate subordinated debentures due with variable interest	$ 85,000,000
Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Interest rate (percent)	3.96%	0.00%
Affiliate Subordinated Debentures Due 2033 [Member]
Debt Instrument [Line Items]
Interest rate (percent)	6.52%	5.68%
FHLB loan due and issued with fixed interest, Senior notes due and issued with fixed interest and Affiliate subordinated debentures due with variable interest	$ 15,500,000.0
Reported Value Measurement [Member]
Debt Instrument [Line Items]
Total notes payable	122,000,000.0	$ 122,100,000
Reported Value Measurement [Member] | Federal Home Loan Bank Advances [Member]
Debt Instrument [Line Items]
Total notes payable	21,500,000	21,500,000
Reported Value Measurement [Member] | Federal Home Loan Bank of Cincinnati [Member]
Debt Instrument [Line Items]
Total notes payable	0	85,400,000
Reported Value Measurement [Member] | Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Total notes payable	85,300,000	0
Reported Value Measurement [Member] | Affiliate Subordinated Debentures Due 2033 [Member]
Debt Instrument [Line Items]
Total notes payable	15,200,000	15,200,000
Estimate of Fair Value Measurement [Member]
Debt Instrument [Line Items]
Total notes payable	122,200,000	121,800,000
Estimate of Fair Value Measurement [Member] | Federal Home Loan Bank Advances [Member]
Debt Instrument [Line Items]
Total notes payable	20,600,000	20,900,000
Estimate of Fair Value Measurement [Member] | Federal Home Loan Bank of Cincinnati [Member]
Debt Instrument [Line Items]
Total notes payable	0	85,700,000
Estimate of Fair Value Measurement [Member] | Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Total notes payable	86,400,000	0
Estimate of Fair Value Measurement [Member] | Affiliate Subordinated Debentures Due 2033 [Member]
Debt Instrument [Line Items]
Total notes payable	$ 15,200,000	$ 15,200,000