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Revenue - Narrative (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Revenue from Contract with Customer [Abstract]    
Contract liabilities $ 2,400 $ 2,200
Deferred revenue recognized 1,100 $ 1,500
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01    
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]    
Deferred revenue expected to be recognized $ 1,200  
Performance obligation, expected timing of satisfaction, period 1 year  
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01    
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]    
Deferred revenue expected to be recognized $ 503  
Performance obligation, expected timing of satisfaction, period 1 year  
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01    
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]    
Deferred revenue expected to be recognized $ 759  
Performance obligation, expected timing of satisfaction, period