Postretirement Plans (Net Periodic Benefit Cost Tables) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 100	$ 163	$ 201	$ 326
Interest cost	748	762	1,496	1,526
Expected return on plan assets	(961)	(999)	(1,922)	(1,998)
Amortization of prior service (credits)/costs	(10)	10	(20)	20
Recognized net actuarial loss	201	197	402	394
Settlement/curtailment/other losses		18	1	33
Net periodic benefit cost	78	151	158	301
Net periodic benefit cost included in Earnings from operations	100	463	434	1,092
Other Postretirement Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	27	32	53	64
Interest cost	57	65	114	130
Expected return on plan assets	(2)	(2)	(4)	(4)
Amortization of prior service (credits)/costs	(34)	(31)	(68)	(62)
Recognized net actuarial loss	3	6	6	12
Net periodic benefit cost	51	70	101	140
Net periodic benefit cost included in Earnings from operations	$ 58	$ 62	$ 143	$ 150