Annual report pursuant to Section 13 and 15(d)

Royalty Purchase Agreements - Summary of Acquisition of Royalty Rights (Details)

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Royalty Purchase Agreements - Summary of Acquisition of Royalty Rights (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]    
Balance at beginning of period $ 34,375 $ 15,000
Balance at end of period 34,575 34,375
Agenus    
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]    
Cash receipts for achievement of contractual milestones (1,000)  
Bioasis Technologies Inc    
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]    
Acquisition of royalty rights $ 1,200 375
Aronora    
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]    
Acquisition of royalty rights   9,000
Palobiofarma, S.L.    
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]    
Acquisition of royalty rights   $ 10,000