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Stockholders' Equity - Additional Information (Detail) - USD ($)
 1 Months Ended 12 Months Ended
Sep. 30, 2019
Jun. 30, 2019
Nov. 30, 2018
Jun. 30, 2018
Jun. 30, 2017
Aug. 31, 2016
Jun. 30, 2016
Jan. 31, 2016
Jun. 30, 2015
Dec. 31, 2012
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2010
Class of Stock [Line Items]                            
Net proceeds from sale of common stock $ 271,500,000   $ 298,500,000     $ 215,900,000   $ 281,600,000     $ 371,847,000 $ 306,647,000 $ 31,188,000  
Issuance of common stock in public offering, net of issuance costs (in shares) 7,187,500   18,602,941     6,969,696   10,344,827   19,000,000        
Common stock, par value                     $ 0.0001 $ 0.0001    
Value of shares purchased by Baker Entities in public offerings                     $ 15,000 $ 14,000    
Proceed from sale of stock and warrants                   $ 80,500,000        
Common stock sale price per share                   $ 4.43        
Warrants issued                   500,000        
Warrants issuance price per share                   $ 4.42        
Warrant exercise price                   $ 0.01        
Issuance of warrant value                   $ 2,200,000        
Warrants outstanding                   500,000 493,145      
Description of warrant                     Per their terms, the warrants to purchase 500,000 shares of common stock, of which 493,145 remained outstanding at December 31, 2019, may not be exercised if the holder’s ownership of the Company’s common stock would exceed 19.99 percent following such exercise.      
Options vesting period                     4 years      
Closing market price of Common stock                     $ 42.78      
Aggregate intrinsic value of stock options exercised                     $ 56,600,000 $ 11,200,000 $ 24,400,000  
Cash received from options exercised                     $ 96,000,000.0      
Weighted average per share fair value of options granted                     $ 15.97 $ 12.14 $ 21.11  
Unrecognized compensation costs                     $ 119,300,000      
Weighted average period cost expected to be recognized                     2 years 9 months 18 days      
Issuance of common stock pursuant to employee stock purchase plan                     $ 4,411,000 $ 3,682,000 $ 4,522,000  
Stock Options | Equity Incentive Plan 2010                            
Class of Stock [Line Items]                            
Exercise price of Options as percentage of fair market value                           100.00%
Options maximum expiration term                           10 years
Options vesting period                           4 years
Number of common stock authorized for issuance                     31,254,090      
Common stock available for grants                     12,381,699      
Common stock reserved for issuance under stock purchase plan   8,300,000   6,700,000 5,500,000   3,000,000   5,000,000          
Stock Options | Equity Incentive Plan 2004                            
Class of Stock [Line Items]                            
Exercise price of Options as percentage of fair market value                     100.00%      
Options vesting period                     4 years      
Number of common stock authorized for issuance   600,000                        
Number of periods additional number of shares could be added to shares authorized for issuance                     10 years      
Restricted Stock Units                            
Class of Stock [Line Items]                            
Unrecognized compensation costs                     $ 22,700,000      
Weighted average period cost expected to be recognized                     3 years 9 months 18 days      
Weighted average grant date fair value, Granted                     $ 25.22 $ 21.07    
Employee Stock Purchase Plan                            
Class of Stock [Line Items]                            
Number of common stock authorized for issuance                     2,525,000      
Common stock reserved for issuance under stock purchase plan             400,000              
Term of ESPP Evergreen Provision                     10 years      
Common stock remained available for issuance pursuant to the Purchase Plan                     485,254      
Eligible employees percentage of earnings withheld to purchase shares under purchase plan                     15.00%      
Purchase price of common stock as percentage of market value                     85.00%      
Issuance of common stock pursuant to employee stock purchase plan                     269,037 233,720 192,402  
Average per share price of stock issued under purchase plan                     $ 16.41 $ 15.75 $ 23.50  
Weighted average per share fair value of purchase rights granted                     $ 14.24 $ 8.25 $ 11.44  
Issuance of common stock pursuant to employee stock purchase plan                     $ 4,400,000 $ 3,700,000 $ 4,500,000  
Registration Rights Agreement                            
Class of Stock [Line Items]                            
Common stock, par value               $ 0.0001            
Expiration period               10 years            
Maximum amount of expense agreed to bear under the agreement               $ 50,000            
Registration Rights Agreement | Baker Brothers Life Sciences L.P.                            
Class of Stock [Line Items]                            
Value of shares purchased by Baker Entities in public offerings $ 62,500,000   $ 200,000,000.0     $ 43,000,000.0   $ 75,000,000.0            
Option To Purchase Additional Shares                            
Class of Stock [Line Items]                            
Issuance of common stock in public offering, net of issuance costs (in shares) 937,500   2,426,470     909,090