Annual report pursuant to Section 13 and 15(d)

Collaboration Agreement - Additional Information (Detail)

v3.6.0.2
Collaboration Agreement - Additional Information (Detail) - USD ($)
 1 Months Ended 3 Months Ended 4 Months Ended 12 Months Ended
Apr. 24, 2015
Jan. 31, 2017
Aug. 31, 2016
Dec. 31, 2009
Jun. 30, 2016
Mar. 31, 2016
Dec. 31, 2015
Sep. 30, 2015
Jun. 30, 2015
Mar. 31, 2015
Apr. 24, 2015
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
May 14, 2015
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]                              
Collaboration revenue         $ 2,122,000 $ 2,940,000 $ 6,024,000 $ 6,737,000 $ 4,025,000 $ 1,374,000   $ 5,062,000 $ 18,160,000 $ 27,116,000  
Subsequent Event [Member]                              
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]                              
Reversion rights period   90 days                          
Ionis Pharmaceuticals Inc. [Member]                              
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]                              
Litigation settlement, upfront payment     $ 1,400,000                        
Royalty payment percentage     5.00%                        
Sale, license or other transaction payment percentage     50.00%                        
Ionis Pharmaceuticals Inc. [Member] | Maximum [Member]                              
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]                              
Litigation settlement, success based payment     $ 5,000,000                        
Collaborative Arrangement [Member] | Teva Pharmaceutical Industries Ltd. [Member]                              
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]                              
Proceeds from advance reimbursement research and development                     $ 27,000,000        
Hold-back amount and third-party expenses deducted from advanced reimbursement payment $ 3,800,000                   3,800,000        
Hold-back amount deducted from advanced reimbursement payment 3,000,000                   3,000,000        
Third-party expenses deducted from advanced reimbursement payment                     $ 800,000        
Maximum cost exposure if third-party agreements discovered after the termination date                       $ 100,000      
Proceeds from advance reimbursement research and development, net amount       $ 50,000,000                      
Collaborative Arrangement [Member] | Ionis Pharmaceuticals Inc. [Member]                              
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]                              
Net proceed from collaboration agreement amount, requested payment percentage                             20.00%
Proceeds from advance reimbursement research and development, net amount $ 23,200,000                            
Hold-back amount, requested payment percentage                             30.00%