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Revenue from Contracts with Customers - Narrative (Details) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2021
Sep. 30, 2020
Revenue from Contract with Customer [Abstract]        
Contract with customer, liability, revenue recognized $ 11 $ 19 $ 100 $ 101