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Fair Values of Financial Instruments - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Fair Value Disclosures [Abstract]    
Gains or losses in earnings attributable to the change in unrealized gains or losses $ 0 $ 0
Carrying value of an impaired loan 10,306,000 4,396,000
Impaired loans, allowance for loan losses 401,000 443,000
Fair value adjustment to OREO due to declines or impairment after foreclosure $ 0 $ 234,042