Stock-Based Compensation - Additional Information (Detail)	Apr. 27, 2017 shares
2015 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation, additional shares authorized	1,200,000
Share based compensation, shares authorized	5,755,277
2017 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation, shares authorized	250,000
Percentage of discount on closing price	15.00%
Employee Stock Purchase Plan, date of implementation	Mar. 10, 2017
Employee Stock Purchase Plan, date of first purchase	Sep. 13, 2017