Postretirement Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 411	$ 350	$ 822	$ 702
Interest cost	751	780	1,502	1,559
Expected return on plan assets	(958)	(935)	(1,916)	(1,870)
Amortization of prior service costs	56	59	112	121
Recognized net actuarial loss	484	314	968	628
Settlement and curtailment loss	3	11	10	55
Net periodic benefit cost	747	579	1,498	1,195
Net periodic benefit cost included in Earnings from operations	593	389	1,248	915
Contributions to postretirement benefit plans			763	0
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	36	36	72	72
Interest cost	79	103	158	206
Expected return on plan assets	(2)	(1)	(4)	(2)
Amortization of prior service costs	(49)	(24)	(98)	(48)
Recognized net actuarial loss	30	33	60	66
Settlement and curtailment loss			(2)
Net periodic benefit cost	94	147	186	294
Net periodic benefit cost included in Earnings from operations	133	118	282	280
Contributions to postretirement benefit plans			$ 8	$ 8