Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity - Additional Information (Detail)

v3.19.3
Stockholders' Equity - Additional Information (Detail) - USD ($)
3 Months Ended 9 Months Ended 12 Months Ended
Jul. 18, 2019
Feb. 25, 2019
Sep. 30, 2019
Jun. 30, 2019
Mar. 31, 2019
Sep. 30, 2018
Jun. 30, 2018
Mar. 31, 2018
Sep. 30, 2019
Sep. 30, 2018
Dec. 31, 2017
Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                        
Authorized capital stock     520,000,000           520,000,000      
Common stock, par value     $ 0.0001           $ 0.0001     $ 0.0001
Common stock, shares authorized     500,000,000           500,000,000     500,000,000
Preferred stock, par value     $ 0.0001           $ 0.0001      
Preferred stock, shares authorized     20,000,000           20,000,000      
Preferred stock, shares outstanding     0           0     0
Proceeds from sale of common stock, net                 $ 12,630,000 $ 47,586,000    
Stock option granted description terms                 the exercise price of an option granted to a 10% shareholder cannot be less than 110% of the estimated fair value of the shares on the date of grant. Options granted generally vest over four years and expire in seven to ten years.      
Ownership percent                 10.00%      
Shares of common stock, reserved for issuance     14,492,765           14,492,765      
Common stock, shares exercised                 192,716 781,191    
Option intrinsic value, exercised                 $ 3,400,000 $ 13,900,000    
Net tax benefits related to exercised options                 0      
Stock purchase, value     $ 160,000 $ 1,802,000 $ 2,898,000 $ 3,671,000 $ 8,661,000 $ 6,196,000        
Stock-based compensation expense     $ 12,152,000     $ 9,252,000     $ 39,622,000 24,264,000    
2014 Equity Incentive Plan                        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                        
Shares of common stock, reserved for issuance     12,101,764           12,101,764      
Aggregate number of awards available for grant to be issued     3,631,948           3,631,948      
Outstanding options and RSUs     8,469,816           8,469,816      
Inducement Plan                        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                        
Shares of common stock, reserved for issuance     1,213,760           1,213,760      
Aggregate number of awards available for grant to be issued     427,436           427,436      
Outstanding options and RSUs     786,324           786,324      
2014 Employee Stock Purchase Plan                        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                        
Percentage of employees purchase price of common stock                 85.00%      
Shares of common stock, reserved for issuance     1,067,575           1,067,575      
Unrecognized stock-based compensation expense     $ 800,000           $ 800,000      
Employee stock purchase plan description                 (i) the beginning of a 12-month offering period, or (ii) at the end of one of the two related 6-month purchase periods      
Stock-based compensation expense                 $ 900,000 $ 500,000    
Shares purchased                 74,439 77,100    
Aggregate number of shares authorized     1,355,973           1,355,973      
Restricted Stock Units (RSUs)                        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                        
Weighted average grant date fair value per share                 $ 27.04 $ 34.61    
Unrecognized stock-based compensation expense     $ 45,400,000           $ 45,400,000      
Unrecognized stock-based compensation weighted average recognition period                 2 years 3 months 18 days      
Aggregate intrinsic value     28,300,000           $ 28,300,000      
Restricted stock units, settled                 562,964 634,851    
RSU settlements, net of shares withheld, shares                 488,964 439,986    
Restricted stock units withheld for tax obligations                 212,879 189,951    
Restricted stock units withheld for tax obligations, value                 $ 6,700,000 $ 7,500,000    
Restricted Stock Units (RSUs) | From Date Of Grant                        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                        
Share based compensation, vesting period                 4 years      
Employees And Non Employees                        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                        
Share based compensation, vesting period                 4 years      
Vested and Unvested Options                        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                        
Unrecognized stock-based compensation weighted average recognition period                 2 years 9 months 18 days      
Stock options, issued                     275,000  
Unrecognized stock-based compensation     $ 75,900,000           $ 75,900,000      
Maximum | 2014 Employee Stock Purchase Plan                        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                        
Stock purchase, value                 $ 25,000      
Annual increase in EIP/ESPP, subject to other limitations                 1.00%      
Maximum increase in number of shares available for issuance                 230,769      
Maximum | Employees And Non Employees                        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                        
Share based compensation award expiration period                 10 years      
Minimum                        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                        
Percentage of employees purchase price of common stock                 100.00%      
Minimum | 10% Shareholder                        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                        
Percentage of employees purchase price of common stock                 110.00%      
Minimum | Employees And Non Employees                        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                        
Share based compensation award expiration period                 7 years      
Underwritten Public Offering                        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                        
Common stock, shares issued 6,871,727                      
Shares issued, price per share $ 15.28                      
Option price to purchase shares $ 15.28                      
Proceeds from sale of common stock, gross $ 150,000,000.0                      
Proceeds from sale of common stock, net $ 140,700,000                      
Exercise of warrants                 $ 0      
Underwritten Public Offering | Warrant                        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                        
Number of warrants issued 2,945,026                      
Warrant, price per share $ 15.2799                      
Number of securities called by each warrant 1                      
Warrants, exercise price $ 0.0001                      
Warrants, term 7 years                      
Maximum ownership Percentage 9.99%                      
Underwritten Public Offering | Warrant | Maximum                        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                        
Maximum ownership Percentage 19.99%                      
Underwritten Public Offering | Warrant | Minimum                        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                        
Prior notice period 61 days                      
At The Market Offering | Cowen                        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                        
Common stock, shares issued     326,897           686,131      
Proceeds from sale of common stock, gross     $ 5,100,000           $ 13,100,000      
Proceeds from sale of common stock, net     $ 5,000,000.0           $ 12,600,000      
Common stock average price     $ 15.77           $ 19.13      
Common stock value remaining to be sold     $ 86,900,000           $ 86,900,000      
At The Market Offering | Maximum | Cowen                        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                        
Common stock aggregate offering price   $ 100,000,000.0                    
Percentage of commission to be paid on gross sales proceeds of common stock sold   3.00%