Annual report pursuant to Section 13 and 15(d)

Fair Value Measurements - Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail)

v3.8.0.1
Fair Value Measurements - Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - Fair Value, Measurements, Recurring [Member] - USD ($)
$ in Thousands
Dec. 31, 2017
Dec. 31, 2016
Assets    
Total assets $ 5,556 $ 15
Cash [Member]    
Assets    
Total assets 1,262 15
Money market securities (cash equivalents) [Member]    
Assets    
Total assets 4,022  
Restricted cash [Member]    
Assets    
Total assets 272  
Level 1 [Member]    
Assets    
Total assets 5,556 15
Level 1 [Member] | Cash [Member]    
Assets    
Total assets 1,262 $ 15
Level 1 [Member] | Money market securities (cash equivalents) [Member]    
Assets    
Total assets 4,022  
Level 1 [Member] | Restricted cash [Member]    
Assets    
Total assets $ 272