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Stock Based Compensation - Share-based Compensation Arrangement by Share-based Payment Award (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award      
Shares available for grants under the plans 10,439,355    
Compensation cost for all grants of shares and units $ 10 $ 27 $ 18