Employee Benefit Plans - Components of Net Periodic Benefit Cost (Benefit) and Other Amounts Recognized in Other Comprehensive Income (Loss), Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Employer contributions [1]	$ 70	$ 70
Other Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Employer contributions [1]	$ 5	$ 0