Annual report pursuant to Section 13 and 15(d)

Commitment and Contingencies - Additional Information (Details)

v3.19.1
Commitment and Contingencies - Additional Information (Details) - USD ($)
$ in Millions
 1 Months Ended 12 Months Ended 19 Months Ended
May 31, 2016
Mar. 31, 2015
Dec. 31, 2014
Aug. 31, 2013
Aug. 31, 2012
May 31, 2012
May 31, 2011
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Dec. 01, 2017
Other Commitments [Line Items]                      
Rent expense               $ 3.6 $ 3.2 $ 2.2  
South San Francisco Facility                      
Other Commitments [Line Items]                      
Tenant improvement allowance           $ 0.9         $ 0.2
Tenant allowance repayable period 2021-11         2016-11          
Option to extend lease term 2026-11                    
South San Francisco Facility | Minimum                      
Other Commitments [Line Items]                      
Lessee operating lease fixed rental payment period 2016-12                    
South San Francisco Facility | Maximum                      
Other Commitments [Line Items]                      
Lessee operating lease fixed rental payment period 2021-11                    
San Carlos California Facility | California                      
Other Commitments [Line Items]                      
Lessee operating lease fixed rental payment period         2016-07            
Option to extend lease term     2027-07                
Initial operating lease agreement period             2011-05        
Lease, extended lease term     2021-07                
Description of options to extend the lease term               Two three-year options to extend the lease term.      
Second Facility in South San Francisco | California                      
Other Commitments [Line Items]                      
Initial operating sublease agreement period       2013-08              
Lessee operating sublease fixed rental payment periods       2017-03              
Operating sublease option to extend lease term 2026-11                    
Second Facility in South San Francisco | Minimum | California                      
Other Commitments [Line Items]                      
Lessee operating sublease fixed rental payment periods 2017-05                    
Second Facility in South San Francisco | Maximum | California                      
Other Commitments [Line Items]                      
Lessee operating sublease fixed rental payment periods 2021-11                    
Second Facility in San Carlos | California                      
Other Commitments [Line Items]                      
Lessee operating lease fixed rental payment period   2021-06                  
Option to extend lease term   2027-06                  
Initial operating lease agreement period   2015-03                  
Description of options to extend the lease term               Two three-year options to extend the lease term.