Employee Benefit Plans (Retirement Plan Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Settlement charges	$ 0	$ 0	$ 117
Defined contribution plans	54	58	50
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost (benefits earned during the period)	61	58	66
Interest cost	70	82	93
Expected return on plan assets	(126)	(115)	(146)
Settlement charges	0	96	117
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Curtailment	0	0	(1)
Amortization of actuarial loss	38	26	55
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	(19)	(19)	(19)
Net periodic defined benefit plan expense	24	128	165
Pension Expense	78	186	215
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost (benefits earned during the period)	1	2	2
Interest cost	4	5	5
Settlement charges	0	3
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Curtailment	0	0	0
Amortization of actuarial loss	6	4	3
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	(13)	(15)	(15)
Net periodic defined benefit plan expense	(2)	(1)	(5)
Pension Expense	$ (2)	$ (1)	$ (5)