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Income Taxes (Details) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2021
Mar. 31, 2020
Income Tax Disclosure [Abstract]    
Effective tax rate (percent) 20.60% 166.70%
Change in amount of valuation allowance $ 52  
Worthless stock deduction 11  
Unrecognized tax benefits, portion expected to be resolved in the next fiscal year 57  
Unrecognized tax benefits that would impact effective tax rate $ 55