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Share-Based Compensation - Additional Share Based Compensation Information (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Share-based Payment Arrangement [Abstract]      
Total intrinsic value of options exercised and shares vested $ 41 $ 21 $ 27
Fair value of shares vested 42 23 26
Cash received from share award exercises 0 0 2
Tax benefit of options exercised and shares vested $ 0 $ 0 $ 0