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Stock-Based Compensation - Summary of Restricted Stock Units Activity (Detail) - Restricted Stock Units (RSUs) [Member]
9 Months Ended
Sep. 30, 2017
USD ($)
$ / shares
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Nonvested Number, Beginning balance | shares 1,067,557
Number, Granted | shares 331,250
Number, Vested, including shares withheld to cover taxes | shares (413,807)
Number, Forfeited | shares (58,900)
Nonvested Number, Ending balance | shares 926,100
Nonvested Weighted Average Grant Date Fair Value, Beginning balance | $ / shares $ 25.37
Weighted Average Grant Date Fair Value, Granted | $ / shares 44.29
Weighted Average Grant Date Fair Value, Vested, including shares withheld to cover taxes | $ / shares 24.69
Weighted Average Grant Date Fair Value, Forfeited | $ / shares 30.94
Nonvested Weighted Average Grant Date Fair Value, Ending balance | $ / shares $ 32.13
Fair Value, Vested, including shares withheld to cover taxes | $ $ 18,258,878
Fair Value, Nonvested at end of period | $ $ 42,526,512