v3.19.3.a.u2
Related Party Transactions - Additional Information (Detail) - USD ($)
$ in Millions
1 Months Ended
Apr. 26, 2017
May 31, 2019
Nov. 30, 2018
Mar. 31, 2017
Dec. 31, 2019
Dec. 31, 2018
Apr. 30, 2017
Related Party Transaction [Line Items]              
Unpaid principal balance of convertible senior note due to related parties         $ 3 $ 3  
Chief Executive Officer [Member]              
Related Party Transaction [Line Items]              
Common stock shares issued   102,880   95,420      
Issuance of common stock public offering price   $ 25   $ 25      
Chief Executive Officer [Member] | Private Placement [Member]              
Related Party Transaction [Line Items]              
Common stock shares issued     56,915        
Issuance of common stock public offering price     $ 20        
Chief Executive Officer [Member] | Zero-Coupon Convertible Senior Notes due in 2020 [Member] | Recourse debt [Member]              
Related Party Transaction [Line Items]              
Principal amount of convertible senior notes             $ 10
Convertible instrument, shares issued 33,333            
Conversion feature of Convertible Senior Notes $ 10