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)

v3.19.1
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, 2018
Dec. 31, 2017
Assets    
Total assets $ 14,654 $ 5,556
Cash [Member]    
Assets    
Total assets 1,070 1,262
Money market securities (cash equivalents) [Member]    
Assets    
Total assets 8,445 4,022
Restricted cash [Member]    
Assets    
Total assets 50 272
Corporate bonds and commercial paper (short term investments) [Member]    
Assets    
Total assets 5,089  
Level 1 [Member]    
Assets    
Total assets 9,565 5,556
Level 1 [Member] | Cash [Member]    
Assets    
Total assets 1,070 1,262
Level 1 [Member] | Money market securities (cash equivalents) [Member]    
Assets    
Total assets 8,445 4,022
Level 1 [Member] | Restricted cash [Member]    
Assets    
Total assets 50 $ 272
Level 2 [Member]    
Assets    
Total assets 5,089  
Level 2 [Member] | Corporate bonds and commercial paper (short term investments) [Member]    
Assets    
Total assets $ 5,089