Postretirement Plans (Components Of Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 402	$ 604	$ 1,764
Interest cost	2,991	3,050	2,990
Expected return on plan assets	(3,847)	(3,999)	(4,031)
Amortization of prior service (credits)/costs	(39)	38	196
Recognized net actuarial loss	804	790	1,577
Settlement/curtailment/other losses	1	40	290
Net periodic benefit cost	312	523	2,786
Net periodic benefit cost included in Earnings from operations	639	1,979	2,366
Other Postretirement Benefits Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	106	128	140
Interest cost	229	262	248
Expected return on plan assets	(7)	(8)	(8)
Amortization of prior service (credits)/costs	(137)	(126)	(136)
Recognized net actuarial loss	10	22	31
Settlement/curtailment/other losses			10
Net periodic benefit cost	201	278	285
Net periodic benefit cost included in Earnings from operations	$ 262	$ 274	$ 288