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Revenue - Additional Information (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Revenue from Contract with Customer [Abstract]      
Contract liabilities $ 1,381 $ 1,236 $ 1,368
Revenues relating to contract liabilities outstanding $ 463 $ 508 $ 544