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Share-Based Compensation - Additional Information (Detail)
3 Months Ended 9 Months Ended
Sep. 30, 2017
USD ($)
shares
Sep. 30, 2017
USD ($)
shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Common stock, authorized shares 6,000,000,000 6,000,000,000
2017 Employee Plan [Member]    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Shares of common stock reserved for future issuance 6,606,181 6,606,181
Compensation expense | $ $ 4,000,000 $ 11,000,000
Unrecognized compensation costs related to unvested awards | $ $ 24,000,000 $ 24,000,000
Unrecognized compensation costs related to unvested awards, weighted-average period   1 year 9 months 18 days
2017 Employee Plan [Member] | Maximum [Member]    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Common stock, authorized shares 8,000,000 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 401,128 401,128
2017 Director Plan [Member] | Maximum [Member]    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Common stock, authorized shares 450,000 450,000
Performance Stock Units ("PSUs") [Member]    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Vesting rights   zero to 200%
Performance Stock Units ("PSUs") [Member] | Maximum [Member]    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Share-based compensation arrangement by share-based payment award performance period   3 years
Vesting rights   200%
Performance Stock Units ("PSUs") [Member] | Minimum [Member]    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Share-based compensation arrangement by share-based payment award performance period   2 years
Market capitalization | $ $ 1,000,000,000 $ 1,000,000,000
Vesting rights   0%