Postretirement Plans (Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Other Postretirement Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 32	$ 35	$ 64	$ 70
Interest cost	65	62	130	124
Expected return on plan assets	(2)	(2)	(4)	(4)
Amortization of prior service costs	(31)	(34)	(62)	(68)
Recognized net actuarial loss	6	11	12	15
Settlement/curtailment/other losses		3		5
Net periodic benefit cost	70	75	140	142
Net periodic benefit cost included in Earnings from operations	62	69	150	161
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	163	442	326	884
Interest cost	762	747	1,526	1,494
Expected return on plan assets	(999)	(1,008)	(1,998)	(2,016)
Amortization of prior service costs	10	49	20	98
Recognized net actuarial loss	197	396	394	792
Settlement/curtailment/other losses	18	73	33	111
Net periodic benefit cost	151	699	301	1,363
Net periodic benefit cost included in Earnings from operations	$ 463	$ 523	$ 1,092	$ 1,308