Quarterly report pursuant to Section 13 or 15(d)

Stock-Based Compensation - Stock Options - Additional Information (Detail)

v3.8.0.1
Stock-Based Compensation - Stock Options - Additional Information (Detail)
$ in Millions
9 Months Ended
Sep. 30, 2017
USD ($)
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Total unrecognized stock-based compensation expense related to non-vested stock options $ 6.7
Unrecognized stock-based compensation expense related to non-vested stock options period of recognition 4 years 3 months 19 days
Dividend yield percentage 0.00%
IPO [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of stock options vested | shares 1,159,914
Compensation expense $ 5.6
Minimum [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Stock option, vesting period 2 years
Maximum [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Stock option, vesting period 6 years
Acceleration Vesting [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Percentage of vesting 25.00%