Annual report pursuant to Section 13 and 15(d)

Equity Incentive Plans and Stock Based Compensation - Stock Options Outstanding and Exercisable by Exercise Price (Detail)

v3.8.0.1
Equity Incentive Plans and Stock Based Compensation - Stock Options Outstanding and Exercisable by Exercise Price (Detail)
 12 Months Ended
Dec. 31, 2017
$ / shares
shares
$ 0.42–0.71  
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]  
Range of Exercise Prices $ 0.42
Range of Exercise Prices $ 0.71
Number Outstanding | shares 480,949
Weighted Average Remaining Contractual Life (Years) 2 years 1 month 20 days
Weighted Average Exercise Price $ 0.55
Number Exercisable | shares 480,949
Weighted Average Exercise Price $ 0.55
$ 1.27–1.27  
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]  
Range of Exercise Prices 1.27
Range of Exercise Prices $ 1.27
Number Outstanding | shares 400,412
Weighted Average Remaining Contractual Life (Years) 5 years 7 months 6 days
Weighted Average Exercise Price $ 1.27
Number Exercisable | shares 393,560
Weighted Average Exercise Price $ 1.27
$ 1.85–6.05  
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]  
Range of Exercise Prices 1.85
Range of Exercise Prices $ 6.05
Number Outstanding | shares 328,929
Weighted Average Remaining Contractual Life (Years) 4 years 9 months 3 days
Weighted Average Exercise Price $ 5.26
Number Exercisable | shares 212,849
Weighted Average Exercise Price $ 5.60
$ 7.14–9.40  
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]  
Range of Exercise Prices 7.14
Range of Exercise Prices $ 9.40
Number Outstanding | shares 1,022,197
Weighted Average Remaining Contractual Life (Years) 9 years 8 months 8 days
Weighted Average Exercise Price $ 8.64
Number Exercisable | shares 10,686
Weighted Average Exercise Price $ 7.99
$ 14.30–42.57  
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]  
Range of Exercise Prices 14.30
Range of Exercise Prices $ 42.57
Number Outstanding | shares 277,168
Weighted Average Remaining Contractual Life (Years) 1 year 6 months 10 days
Weighted Average Exercise Price $ 24.49
Number Exercisable | shares 277,168
Weighted Average Exercise Price $ 24.49
$ 45.65–85.25  
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]  
Range of Exercise Prices 45.65
Range of Exercise Prices $ 85.25
Number Outstanding | shares 259,056
Weighted Average Remaining Contractual Life (Years) 1 year 6 months
Weighted Average Exercise Price $ 59.00
Number Exercisable | shares 259,056
Weighted Average Exercise Price $ 59.00
$ 0.42–85.25  
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]  
Range of Exercise Prices 0.42
Range of Exercise Prices $ 85.25
Number Outstanding | shares 2,768,711
Weighted Average Remaining Contractual Life (Years) 5 years 7 months 13 days
Weighted Average Exercise Price $ 12.07
Number Exercisable | shares 1,634,268
Weighted Average Exercise Price $ 14.76