Postretirement Plans (Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 441	$ 415	$ 1,325	$ 1,244
Interest cost	748	758	2,242	2,300
Expected return on plan assets	(1,008)	(1,042)	(3,024)	(3,125)
Amortization of prior service costs	49	44	147	133
Recognized net actuarial loss	392	254	1,184	768
Settlement/curtailment/other losses	83	35	194	372
Net periodic benefit cost	705	464	2,068	1,692
Net periodic benefit cost included in Earnings from operations	529	715	1,837	2,443
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	35	33	105	97
Interest cost	62	72	186	216
Expected return on plan assets	(2)	(2)	(6)	(6)
Amortization of prior service costs	(34)	(36)	(102)	(108)
Recognized net actuarial loss	8	$ 2	23	$ 6
Settlement/curtailment/other losses	4		9
Net periodic benefit cost	73	$ 69	215	$ 205
Net periodic benefit cost included in Earnings from operations	$ 65	$ 71	$ 226	$ 214