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Contract Costs (Details) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2021
Mar. 31, 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 13 6
Amortization (12) (10)
Capitalized contract cost, net at period end $ 99 $ 87