Annual report pursuant to Section 13 and 15(d)

Fair Value Measurements - Derivative Contingently Issuable Warrant liabilities (Detail)

v3.8.0.1
Fair Value Measurements - Derivative Contingently Issuable Warrant liabilities (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]      
Additions $ 9,914 $ 19,089  
Conversion into common shares (1,064)    
Caelum Warrant Liabilities [Member]      
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]      
Beginning balance 0    
Additions 226    
Change in fair value (3)    
Ending balance 223 0  
Avenue [Member] | Convertible Debt [Member]      
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]      
Beginning balance 200 0  
Additions   200  
Conversion into common shares (299)    
Change in fair value 99    
Ending balance 0 200 $ 0
Avenue [Member] | Contingently Issuable Warrants [Member]      
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]      
Beginning balance 302 114  
Additions   0  
Conversion into common shares (750)    
Change in fair value 488 188  
Ending balance 0 302 114
Mustang [Member]      
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]      
Beginning balance 12 0  
Additions   12  
Conversion into common shares (15)    
Change in fair value 3 0  
Ending balance 0 12 0
Mustang [Member] | Contingently Issuable Warrants [Member]      
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]      
Beginning balance 0 0  
Additions   634  
Conversion into common shares   (793)  
Change in fair value   159  
Ending balance   0 0
Checkpoint [Member] | Contingently Issuable Warrants [Member]      
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]      
Beginning balance   0 0
Additions     175
Conversion into common shares     (613)
Change in fair value     438
Ending balance     0
Helocyte [Member]      
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]      
Beginning balance 167 0  
Additions   428  
Change in fair value (80) (261)  
Ending balance 87 167 0
Helocyte [Member] | Convertible Debt [Member]      
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]      
Beginning balance 4,487 0  
Additions   4,409  
Change in fair value 213 78  
Ending balance 4,700 4,487 $ 0
Caelum Convertible Notes [Member]      
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]      
Beginning balance 0    
Additions 9,914    
Change in fair value 145    
Ending balance $ 10,059 $ 0