Employee Benefit Plans - Schedule of Pre-tax Change in Other Comprehensive Loss (Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Benefits
Recognized in the Balance Sheet
Losses (Gains)	$ 28	$ 21
Expense (Income) Recognized in the Income Statement
Amortization of Net Loss	54	30	$ 41
Settlement Gain	(1)	0	(1)
Amortization of Prior Service Costs	0	0	0
Post-retirement Benefits
Recognized in the Balance Sheet
Losses (Gains)	(11)	22
Expense (Income) Recognized in the Income Statement
Amortization of Net Loss	1	0	0
Settlement Gain	0	0	0
Amortization of Prior Service Costs	$ (7)	$ (7)	$ (2)