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Earnings Per Share - Additional Information (Detail) - shares
3 Months Ended 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Earnings Per Share, Basic and Diluted, Other Disclosures [Abstract]        
Shares of common stock outstanding 5,020,021 5,123,186 5,051,306 5,123,186