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Contract Costs (Details) - USD ($)
$ in Millions
6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Revenue from Contract with Customer [Abstract]    
Capitalized contract cost, amortization period 4 years  
Capitalized Contract Cost, Net [Roll Forward]    
Capitalized contract cost, net at period start $ 98 $ 91
Capitalized 20 14
Amortization (21) (17)
Capitalized contract cost, net at period end $ 97 $ 88