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Stockholders' Equity - Additional Information (Details) - USD ($)
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Jan. 01, 2019
Equity, Class of Treasury Stock [Line Items]        
Stock repurchase program, remaining authorized amount $ 1,600,000,000      
Aggregate reduction in common stock and additional paid-in capital during stock repurchases 8,000,000 $ 15,000,000 $ 0  
Amount charged to retained earnings during stock repurchases 126,000,000 $ 255,000,000 $ 0  
Common stock        
Equity, Class of Treasury Stock [Line Items]        
Stock repurchase program, authorized amount $ 7,500,000,000      
Stock Repurchase Program, increased to authorized amount       $ 2,000,000,000.0