Postretirement Plans (Details) (USD $) In Millions, unless otherwise specified			3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended	9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2012 Pension Plans, Defined Benefit [Member]	Sep. 30, 2011 Pension Plans, Defined Benefit [Member]	Sep. 30, 2012 Pension Plans, Defined Benefit [Member]	Sep. 30, 2011 Pension Plans, Defined Benefit [Member]	Sep. 30, 2012 Other Postretirement Benefit Plans, Defined Benefit [Member]	Sep. 30, 2011 Other Postretirement Benefit Plans, Defined Benefit [Member]	Sep. 30, 2012 Other Postretirement Benefit Plans, Defined Benefit [Member]	Sep. 30, 2011 Other Postretirement Benefit Plans, Defined Benefit [Member]	Sep. 30, 2011 Other Postretirement Benefit Plans, Defined Benefit [Member] Postretirement Plan Adjustment [Member]	Sep. 30, 2011 Other Postretirement Benefit Plans, Defined Benefit [Member] Postretirement Plan Adjustment [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost			$ 411	$ 351	$ 1,233	$ 1,053	$ 36	$ 110	$ 108	$ 182	$ 73	$ 73
Interest cost			751	780	2,253	2,339	79	171	237	377	68	68
Expected return on plan assets			(958)	(935)	(2,874)	(2,805)	(2)	(2)	(6)	(4)
Amortization of prior service costs			56	61	168	182	(49)	(24)	(147)	(72)
Recognized net actuarial loss			484	314	1,452	942	30	76	90	142	(43)	(43)
Settlement and curtailment loss/(gain)				9	10	64			(2)
Net periodic benefit cost			744	580	2,242	1,775	94	331	280	625	184	184
Net periodic benefit cost included in Earnings from operations			583	389	1,831	1,304	132	281	414	561	161	161
Defined Benefit Plan, Benefit Obligation											294	294
Portion of additional net periodic benefit cost remaining in inventory	36,817	32,240									23	23
Contributions to postretirement benefit plans					$ 1,513	$ 500			$ 11	$ 12