Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity (Detail)

v3.19.3
Stockholders' Equity (Detail)
$ / shares in Units, $ in Thousands
 1 Months Ended 9 Months Ended
May 23, 2019
USD ($)
$ / shares
shares
Jun. 30, 2018
USD ($)
shares
Mar. 31, 2018
shares
Jan. 31, 2018
USD ($)
shares
Sep. 30, 2019
USD ($)
Sep. 30, 2018
USD ($)
Dec. 31, 2018
USD ($)
Class of Stock [Line Items]              
Aggregate purchase price, net of offering costs   $ 115,200          
Number of shares for purchase under warrant (in shares) | shares 1,500,000            
Common stock purchase price (in dollars per share) | $ / shares $ 10.00            
Warrant term (in years) 5 years            
Fair value of warrant $ 3,300            
Number of shares sold in transaction (in shares) | shares   12,000,000.0          
Deferred engineering costs         $ 96,497   $ 69,000
Conversion ratio         1    
Fees and commissions   $ 3,600     $ 0 $ 4,090  
Over-allotment Option              
Class of Stock [Line Items]              
Aggregate purchase price, net of offering costs       $ 14,500      
Number of shares sold in transaction (in shares) | shares   1,800,000   1,500,000      
Fees and commissions       $ 500      
Maximum | At-the-Market Program              
Class of Stock [Line Items]              
Aggregate purchase price, net of offering costs         $ 189,700    
Driftwood Project              
Class of Stock [Line Items]              
Deferred engineering costs             $ 50,000
Driftwood Project | Convertible Preferred Stock              
Class of Stock [Line Items]              
Number of shares sold in transaction (in shares) | shares     6,100,000