Postretirement Plans (Components Of Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 3	$ 2	$ 430
Interest cost	2,455	2,925	2,781
Expected return on plan assets	(3,756)	(3,863)	(4,009)
Amortization of prior service credits	(80)	(79)	(56)
Recognized net actuarial loss/(gain)	1,032	643	1,130
Settlement/curtailment loss/(gain)	9		44
Net periodic benefit (income)/cost	(337)	(372)	320
Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	89	77	94
Interest cost	130	196	194
Expected return on plan assets	(9)	(8)	(8)
Amortization of prior service credits	(38)	(35)	(126)
Recognized net actuarial loss/(gain)	(63)	(46)	(10)
Settlement/curtailment loss/(gain)	(4)
Net periodic benefit (income)/cost	105	184	144
Operating Income (Loss) [Member] | Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (income)/cost included in (Loss)/earnings before income taxes	(3)	(313)	(313)
Operating Income (Loss) [Member] | Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (income)/cost included in (Loss)/earnings before income taxes	(91)	(88)	(84)
Other Income [Member] | Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (income)/cost included in (Loss)/earnings before income taxes	(340)	(374)	(143)
Other Income [Member] | Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (income)/cost included in (Loss)/earnings before income taxes	(16)	(107)	(101)
Operating Income (Loss) Before Taxes [Member] | Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (income)/cost included in (Loss)/earnings before income taxes	(337)	(61)	(170)
Operating Income (Loss) Before Taxes [Member] | Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (income)/cost included in (Loss)/earnings before income taxes	$ (107)	$ (195)	$ (185)