Quarterly report pursuant to Section 13 or 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
 3 Months Ended
Mar. 31, 2018
Dec. 31, 2017
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]    
Payment of convertible notes $ (1,858)  
National [Member]    
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]    
Fair value at the beginning of period: 6,671 $ 5,597
Change in fair value   1,074
Fair value at end of period:   6,671
Helocyte [Member]    
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]    
Fair value at the beginning of period: 87  
Change in fair value (9)  
Fair value at end of period: 78 87
Helocyte [Member] | Convertible Debt [Member]    
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]    
Fair value at the beginning of period: 4,700  
Payment of convertible notes (1,858)  
Change in fair value (331)  
Fair value at end of period: 2,511 4,700
National Warrant Liabilities [Member]    
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]    
Fair value at the beginning of period: 686 548
Change in fair value   138
Fair value at end of period:   686
Caelum Convertible Notes [Member]    
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]    
Fair value at the beginning of period: 10,059  
Change in fair value 81  
Fair value at end of period: $ 10,140 $ 10,059