Quarterly report pursuant to Section 13 or 15(d)

Custirsen Collaboration Agreement - Additional Information (Detail)

v3.5.0.2
Custirsen Collaboration Agreement - Additional Information (Detail) - USD ($)
 1 Months Ended 3 Months Ended 4 Months Ended 9 Months Ended
Apr. 24, 2015
Aug. 31, 2016
Dec. 31, 2009
Sep. 30, 2016
Sep. 30, 2015
Apr. 24, 2015
Sep. 30, 2016
Sep. 30, 2015
May 14, 2015
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]                  
Collaboration revenue       $ 0 $ 6,737,000   $ 5,062,000 $ 12,136,000  
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%