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Revenue Recognition - Narrative (Details) - USD ($)
$ in Millions
6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Disaggregation of Revenue [Line Items]    
Contract with customer, liability, revenue recognized $ 371 $ 666
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-04-01    
Disaggregation of Revenue [Line Items]    
Revenue, remaining performance obligation, expected timing of satisfaction, period 3 years