v3.10.0.1
Earnings Per Common Share - Reconciliation of Numerators and Denominators of Basic and Diluted Earnings Per Share (Parenthetical) (Detail) - shares
3 Months Ended 6 Months Ended
Jun. 30, 2017
Jun. 30, 2017
Jun. 30, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]      
Shares subject to stock options, outstanding     0
Employee Stock Option [Member]      
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]      
Antidilutive securities excluded from computation of earnings per common share 39,000 39,000