Employee Benefit Plans (Retirement Plan Expense) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Settlement charges		$ 0	$ 117	$ 0
Defined contribution plans		58	50	57
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost (benefits earned during the period)		58	66	78
Interest cost		82	93	106
Expected return on plan assets		(115)	(146)	(145)
Settlement charges	$ 117	96	117	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Curtailment		0	(1)	0
Amortization of actuarial loss		26	55	65
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)		(19)	(19)	(7)
Net periodic defined benefit plan expense		128	165	97
Pension Expense		186	215	154
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost (benefits earned during the period)		2	2	2
Interest cost		5	5	6
Settlement charges		3
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Curtailment		0	0	0
Amortization of actuarial loss		4	3	4
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)		(15)	(15)	(13)
Net periodic defined benefit plan expense		(1)	(5)	(1)
Pension Expense		$ (1)	$ (5)	$ (1)