v3.19.3
Redeemable Convertible Preferred Stock, Common Stock, and Equity (Deficit) - SAR and Option Activity (Details)
$ / shares in Units, shares in Thousands, $ in Millions
 9 Months Ended 12 Months Ended
Sep. 30, 2019
USD ($)
$ / shares
shares
Dec. 31, 2018
USD ($)
$ / shares
shares
Share-Based Compensation Arrangement By Share-Based Payment Award, Options And Equity Instruments Other Than Options, Nonvested, Number Of Shares [Abstract]    
Weighted-Average Exercise Price Per Share, Outstanding (in dollars per share) | $ / shares $ 9.22  
Weighted-Average Exercise Price Per Share, Awards granted (in dollars per share) | $ / shares 43.00  
Weighted-Average Exercise Price Per Share, Awards exercised (in dollars per share) | $ / shares 2.55  
Weighted-Average Exercise Price Per Share, Awards canceled and forfeited (in dollars per share) | $ / shares 33.19  
Weighted-Average Exercise Price Per Share, Outstanding (in dollars per share) | $ / shares 8.89 $ 9.22
Weighted-Average Exercise Price Per Share, Vested and expected to vest (in dollars per share) | $ / shares 4.58  
Weighted-Average Exercise Price Per Share, Exercisable (in dollars per share) | $ / shares $ 4.58  
Share-Based Compensation Arrangement By Share-based Payment Award, Options And Equity Instruments Other Than Options, Nonvested, Additional Disclosures [Abstract]    
Weighted-Average Contractual Life, Outstanding 4 years 10 months 20 days 5 years 8 months 26 days
Weighted-Average Contractual Life, Vested and expected to vest 4 years 7 months 17 days  
Weighted-Average Contractual Life, Exercisable 4 years 7 months 17 days  
Aggregate Intrinsic Value, Outstanding | $ $ 934 $ 1,456
Aggregate Intrinsic Value, Vested and expected to vest | $ 933  
Aggregate Intrinsic Value, Exercisable | $ $ 933  
SARs    
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]    
Shares outstanding (in shares) 758  
Awards granted (in shares) 86  
Awards exercised (in shares) 0  
Awards canceled and forfeited (in shares) (13)  
Shares outstanding (in shares) 831 758
Vested and expected to vest (in shares) 648  
Exercisable (in shares) 648  
Stock options    
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]    
Options outstanding (in shares) 42,936  
Awards granted (in shares) 250  
Awards exercised (in shares) (1,272)  
Awards canceled and forfeited (in shares) (1,382)  
Options outstanding (in shares) 40,532 42,936
Vested and expected to vest (in shares) 35,145  
Exercisable (in shares) 35,145