Quarterly report pursuant to Section 13 or 15(d)

Collaboration Agreement - Additional Information (Detail)

v3.5.0.2
Collaboration Agreement - Additional Information (Detail) - USD ($)
 1 Months Ended 3 Months Ended 4 Months Ended 6 Months Ended
Aug. 01, 2016
Apr. 24, 2015
Dec. 31, 2009
Jun. 30, 2016
Jun. 30, 2015
Apr. 24, 2015
Jun. 30, 2016
Jun. 30, 2015
May 14, 2015
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]                  
Collaboration revenue       $ 2,122,000 $ 4,025,000   $ 5,062,000 $ 5,399,000  
Ionis Pharmaceuticals Inc. [Member] | Subsequent Event [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] | Subsequent Event [Member]                  
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]                  
Litigation settlement, success based payment $ 5,000,000                
Sale, license or other transaction payment percentage 50.00%                
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. and University of British Columbia [Member]                  
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]                  
Milestone payment due             $ 20,000,000    
Period of milestone payment             21 days    
Reserve for contingency of non payment of non-royalty milestone amount       20,000,000     $ 20,000,000    
Milestone payment made       10,000,000     10,000,000    
Balance amount of milestone payment       10,000,000     $ 10,000,000    
Collaborative Arrangement [Member] | Ionis Pharmaceuticals Inc. and University of British Columbia [Member] | Minimum [Member]                  
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]                  
Percentage of net sales required to be paid as royalty to third party             4.00%    
Collaborative Arrangement [Member] | Ionis Pharmaceuticals Inc. and University of British Columbia [Member] | Maximum [Member]                  
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]                  
Percentage of net sales required to be paid as royalty to third party             8.00%    
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%
Amount due to Ionis for reimbursement for research and development activities       0     $ 0    
Milestone payment due             $ 20,000,000    
Period of milestone payment             21 days    
Reserve for contingency of non payment of non-royalty milestone amount       20,000,000     $ 20,000,000    
Milestone payment made       10,000,000     10,000,000    
Balance amount of milestone payment       $ 10,000,000     $ 10,000,000