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Stock-Based Compensation - Details of Nonvested Restricted Stock Units Activity (Detail) - Restricted stock units
6 Months Ended
Jun. 30, 2017
shares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]  
Number of Units Outstanding, Beginning Balance, Nonvested (in shares) 240,574
Number of Units, Granted (in shares) 94,707
Number of Units, Vested (in shares) (117,198)
Number of Units, Canceled (in shares) (7,829)
Number of Units, Accrued dividend equivalents (in shares) 1,293
Number of Units Outstanding, Ending Balance, Nonvested (in shares) 211,547