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Stock Based Awards and Other Equity Instruments - Additional Information (Details) - USD ($)
12 Months Ended
Jun. 05, 2017
Jun. 28, 2013
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Jun. 21, 2018
Dec. 20, 2011
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]              
Capitalized stock based compensation as internal-use software and website development costs     $ 19,000,000 $ 13,000,000 $ 13,000,000    
Common shares registered for issuance under incentive plan             17,500,000
Common stock share issuance under plan   15,000,000          
Cash received from stock option exercises     $ 2,000,000 6,000,000 3,000,000    
Nonqualified stock option award grant date Aug. 28, 2013            
Incremental fair value recognized to stock-based compensation expense $ 5,000,000            
2011 Plan              
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]              
Common shares registered for issuance under incentive plan             17,400,000
Common stock share issuance under plan     0        
2011 Plan | Stock Options              
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]              
Closing stock price     $ 30.38        
Total intrinsic value     $ 2,000,000 20,000,000 8,000,000    
Total fair value of stock options vested     15,000,000 38,000,000 40,000,000    
Cash received from stock option exercises     $ 2,000,000 $ 6,000,000 $ 3,000,000    
Deferred Compensation Plan for Non Employee Directors              
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]              
Common shares registered for issuance under incentive plan             100,000
2018 Plan              
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]              
Common shares registered for issuance under incentive plan           6,000,000  
2018 Plan              
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]              
Number of shares reserved for future stock-based awards under plan     10,100,000