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Basis of Presentation and Significant Accounting Policies Additional Information (Details) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2021
Jun. 30, 2020
Dec. 31, 2020
Derivative [Line Items]        
Stockholders' Equity Attributable to Noncontrolling Interest $ 60 $ 60   $ 60
Preferred Stock, Shares Issued 0 0    
Net Income (Loss) Attributable to Nonredeemable Noncontrolling Interest $ 0 $ 0 $ 0  
Noncontrolling Interest, Change in Redemption Value 1 14    
Business Acquisition, Percentage of Voting Interests Acquired       80.00%
Business Combination, Redeemable Noncontrolling Percentage       20.00%
Xchange        
Derivative [Line Items]        
Redeemable Noncontrolling Interest, Equity, Carrying Amount       $ 7
Redeemable Noncontrolling Interest, Equity, Redemption Value 20 20    
Retained Earnings [Member]        
Derivative [Line Items]        
Noncontrolling Interest, Change in Redemption Value $ 1 $ 14