Annual report pursuant to Section 13 and 15(d)

Stock Plans - Additional Information (Detail)

v3.19.1
Stock Plans - Additional Information (Detail) - USD ($)
 1 Months Ended 12 Months Ended
Jun. 29, 2018
May 31, 2017
Apr. 30, 2017
Dec. 31, 2018
Dec. 31, 2017
Class of Stock [Line Items]          
Stock-based compensation expense       $ 15,493,000 $ 16,089,000
Employee payroll deductions accrued       6,570,000 $ 3,117,000
Chad Steelberg [Member]          
Class of Stock [Line Items]          
Common stock granted         17,807
Restricted Stock Units [Member]          
Class of Stock [Line Items]          
Stock-based compensation expense       427,000 $ 327,000
Restricted Stock [Member]          
Class of Stock [Line Items]          
Stock-based compensation expense       463,000 891,000
Stock Options [Member]          
Class of Stock [Line Items]          
Stock-based compensation expense       $ 10,050,000 $ 14,391,000
2017 Stock Incentive Plan [Member]          
Class of Stock [Line Items]          
Common stock reserved for future issuance     2,000,000 941,827  
Annual shares increase for future issuance by percentage under employee stock purchase plans     3.00%    
2017 Stock Incentive Plan [Member] | Restricted Stock Units [Member]          
Class of Stock [Line Items]          
Vesting period       1 year  
2017 Stock Incentive Plan [Member] | Maximum [Member]          
Class of Stock [Line Items]          
Increase in common stock reserved for future issuance     750,000    
2018 Performance- Based Stock Incentive Plan [Member]          
Class of Stock [Line Items]          
Common stock reserved for future issuance       1,032,675  
Number of shares authorized for issuance       4,200,000  
Vesting period       30 days  
Options exercise price       $ 21.25  
Stock options, expiration period       10 years  
Stock-based compensation expense       $ 3,799,000  
Total grant date fair value of stock options vested $ 30,375,000        
2018 Performance- Based Stock Incentive Plan [Member] | Performance-based Stock Options [Member]          
Class of Stock [Line Items]          
Options exercise price       $ 21.25  
Options granted       3,167,325  
Weighted Average Grant Date Fair Value, Granted       $ 9.59  
Weighted average remaining contractual term       9 years 4 months 6 days  
Total grant date fair value of stock options vested       $ 0  
Cost of share-based compensation awards, recognition period       3 years 10 months 24 days  
Unrecognized compensation expense related to stock options       $ 26,534,000  
2018 Performance- Based Stock Incentive Plan [Member] | Performance-based Stock Options [Member] | Chad Steelberg [Member]          
Class of Stock [Line Items]          
Common stock granted       1,809,900  
2018 Performance- Based Stock Incentive Plan [Member] | Performance-based Stock Options [Member] | Ryan Steelberg [Member]          
Class of Stock [Line Items]          
Common stock granted       1,357,425  
2014 Plan Stock Options/Stock Issuance Plan and 2017 Stock Incentive Plan [Member]          
Class of Stock [Line Items]          
Vesting period       4 years  
Options exercise price       $ 13.19  
Stock options, expiration period       10 years  
Options granted       1,031,091  
Weighted average remaining contractual term       8 years 4 months 28 days 9 years 2 months 1 day
2014 Plan Stock Options/Stock Issuance Plan and 2017 Stock Incentive Plan [Member] | Restricted Stock Units [Member]          
Class of Stock [Line Items]          
Unrecognized cost of share-based compensation awards       $ 362,000  
Cost of share-based compensation awards, recognition period       7 months 6 days  
Weighted Average Grant Date Fair Value, Granted       $ 13.46 $ 14.76
Restricted stock granted       69,198  
Fair value of restricted stock vested       $ 901,000 $ 0
2014 Plan Stock Options/Stock Issuance Plan and 2017 Stock Incentive Plan [Member] | Restricted Stock [Member]          
Class of Stock [Line Items]          
Unrecognized cost of share-based compensation awards       $ 400,000  
Cost of share-based compensation awards, recognition period       1 year 7 months 6 days  
Weighted Average Grant Date Fair Value, Granted         $ 15.47
Restricted stock granted       0  
Fair value of restricted stock vested       $ 1,022 $ 2,185
2014 Plan Stock Options/Stock Issuance Plan and 2017 Stock Incentive Plan [Member] | Stock Options [Member]          
Class of Stock [Line Items]          
Weighted Average Grant Date Fair Value, Granted       $ 7.40 $ 8.95
Total grant date fair value of stock options vested       $ 8,929,000 $ 13,094,000
Cost of share-based compensation awards, recognition period       2 years 3 months 18 days  
Unrecognized compensation expense related to stock options       $ 18,232,000  
Aggregate intrinsic value of the options exercised       $ 1,984,000 1,875,000
2014 Stock Incentive Plan [Member] | Performance-based Stock Options [Member]          
Class of Stock [Line Items]          
Stock-based compensation expense         $ 9,282,000
2014 Stock Incentive Plan [Member] | Performance-based Stock Options [Member] | Chad Steelberg and Ryan Steelberg [Member]          
Class of Stock [Line Items]          
Vesting period   5 years      
Options exercise price   $ 15.00      
Options granted   1,044,818      
Weighted Average Grant Date Fair Value, Granted         $ 8.88
Weighted average remaining contractual term         8 years 4 months 24 days
Vesting rights, market capitalization   $ 400,000      
Vesting rights, consecutive trading days   5 days      
Vesting rights description       The performance-based stock options provided for the awards to vest upon the earlier of the first date on which the market capitalization of the Company’s common stock equaled or exceeded $400,000 over five consecutive business days, or five years after the IPO.  
2014 Stock Incentive Plan [Member] | Timebased Stock Option | Chad Steelberg and Ryan Steelberg [Member]          
Class of Stock [Line Items]          
Vesting period   3 years      
Options exercise price   $ 15.00      
Options granted   2,089,638      
Employee Stock Purchase Plan [Member]          
Class of Stock [Line Items]          
Common stock reserved for future issuance     1,000,000    
Annual shares increase for future issuance by percentage under employee stock purchase plans     1.00%    
Number of shares authorized for issuance     200,000    
ESPP offering description       Under the ESPP, each offering period is generally 24 months with four, six-month purchase intervals, and new offering periods generally commence every six months, as determined by the compensation committee of the Board of Directors.  
Maximum number of shares per employee in each purchase     1,000    
Employee payroll deductions accrued       $ 448,000 $ 253,000
Common stock were purchased under ESPP       80,654  
Weighted average purchase price       $ 12.72  
Employee Stock Purchase Plan [Member] | Maximum [Member]          
Class of Stock [Line Items]          
Increase in common stock reserved for future issuance     250,000    
Employee Stock Purchase Plan [Member] | Minimum [Member]          
Class of Stock [Line Items]          
Percentage of purchase price of common stock fair value     85.00%