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Computation of Earnings Per Share - Additional Information (Detail) - shares
3 Months Ended 6 Months Ended
Jun. 30, 2017
Jun. 30, 2016
Jun. 30, 2017
Jun. 30, 2016
Stock Options [Member]        
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]        
Antidilutive shares excluded from calculation of earnings per share 48,498 60,350 47,679 61,800