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Share-Based Compensation - Additional Information (Detail) - USD ($)
1 Months Ended 3 Months Ended
Feb. 29, 2020
Mar. 31, 2020
Mar. 31, 2019
Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Common stock, authorized shares   6,000,000,000   6,000,000,000
Share-based compensation arrangement by share-based payment award performance period   1 year    
2017 Employee Plan [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Shares of common stock reserved for future issuance   4,490,773    
Compensation expense   $ 2,000,000 $ 4,000,000  
Unrecognized compensation costs related to unvested awards   $ 28,000,000    
Unrecognized compensation costs related to unvested awards, weighted-average period   2 years 1 month 6 days    
Total fair value of shares vested   $ 17,000,000 $ 15,000,000  
2017 Employee Plan [Member] | Maximum [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Common stock, authorized shares   8,000,000    
2017 Director Plan [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Shares of common stock reserved for future issuance   276,521    
2017 Director Plan [Member] | Maximum [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Common stock, authorized shares   450,000    
Performance Stock Units ("PSUs") [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Compensation expense   $ 0    
Share-based compensation arrangement by share-based payment award performance period 1 year 3 years    
Market capitalization   $ 1,000,000,000    
Vesting rights   zero to 200    
Performance Stock Units ("PSUs") [Member] | Tranche Two [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Vesting rights 100%      
Performance Stock Units ("PSUs") [Member] | Maximum [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Vesting rights   200%    
Performance Stock Units ("PSUs") [Member] | Maximum [Member] | Tranche Three [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Vesting rights 200%      
Performance Stock Units ("PSUs") [Member] | Minimum [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Vesting rights   0%    
Performance Stock Units ("PSUs") [Member] | Minimum [Member] | Tranche One [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Vesting rights 0%