Employee Benefit Plans (Components of Net Periodic Pension (Income) Expense) (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Aug. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Net settlement, curtailment and special termination benefits (gain) loss	$ (98)
Non-service pension benefit		$ (902)	$ (829)	$ (659)
Net periodic pension and other postretirement (income) expense		(413)	(566)	(392)
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost		483	261	265
Interest cost		1,650	1,245	1,058
Expected return on plan assets		(2,995)	(2,252)	(2,061)
Amortization of prior service cost (credit)		51	16	(42)
Recognized actuarial net loss		337	245	373
Net settlement, curtailment and special termination benefits (gain) loss		45	(59)	3
Non-service pension benefit		(912)	(805)	(669)
Net periodic pension and other postretirement (income) expense		$ (429)	$ (544)	$ (404)