Quarterly report pursuant to Section 13 or 15(d)

Collaboration Arrangements - Additional Information (Detail)

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Collaboration Arrangements - Additional Information (Detail) - Merck KGaA - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2016
Jun. 30, 2015
Jun. 30, 2016
Jun. 30, 2015
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]        
Upfront and milestone payments received to date     $ 110.0  
Revenue recognized by the Company $ 0.0 $ 3.7 0.0 $ 7.4
Company received a reimbursement for eligible worldwide development expenses $ 0.9 $ 3.6 $ 1.7 $ 5.6
Collaborative Arrangement Product Agreement | Evofosfamide        
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]        
Merck KGaA's percentage share of worldwide development expenses     70.00%