Annual report pursuant to Section 13 and 15(d)

Commitments and Contingencies (Narrative) (Detail)

v3.8.0.1
Commitments and Contingencies (Narrative) (Detail)
 1 Months Ended 2 Months Ended 5 Months Ended 6 Months Ended
Nov. 30, 2016
USD ($)
security_offering
Jan. 31, 2016
USD ($)
underwriter
Nov. 30, 2015
USD ($)
security_offering
firm
claim
May 31, 2014
USD ($)
employee
Jul. 31, 2013
USD ($)
plaintiff
Jan. 31, 2015
claim
May 31, 2017
USD ($)
claim
Dec. 31, 2017
USD ($)
claim
Dec. 31, 2016
USD ($)
Loss Contingencies [Line Items]                  
Thereafter               $ 36,569,000  
Deferred rent               2,151,000 $ 1,764,000
Number of firms that underwrote security offerings | firm     9            
Number of security offerings | security_offering     6            
Accrued liabilities               6,902,000 $ 4,396,000
Convertible Notes Payable                  
Loss Contingencies [Line Items]                  
Offering         $ 300,000,000        
Common Stock                  
Loss Contingencies [Line Items]                  
Offering       $ 1,656,000          
Ladenburg                  
Loss Contingencies [Line Items]                  
New claims filed | claim             5    
Number of underwriters | underwriter   1              
Compensatory damages                  
Loss Contingencies [Line Items]                  
New claims filed | claim     2     2      
Number of plaintiffs | employee       17          
Damages sought by plaintiff     $ 151,000,000       $ 5,400,000 $ 300,000  
Claims settled | claim               4  
Compensatory damages | Ladenburg                  
Loss Contingencies [Line Items]                  
Damages sought by plaintiff $ 105,000,000 $ 2,900,000,000              
Number of security offerings | security_offering 2                
ARCP July 2013 Offering | Compensatory damages                  
Loss Contingencies [Line Items]                  
Number of plaintiffs | plaintiff         8