Retirement Benefits (Details 2) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Changes in Unamortized Benefit plan Costs (Table Amounts) [Abstract]
Change in net actuarial loss	$ 2,504	$ 2,825	$ (222)
Change in prior service cost	(2)	(602)
Amortization of:
Prior service credit	109	28	12
Net loss from previous years	(448)	(179)	(270)
Tax benefit related to above items	(860)	(823)	183
Change in unamortized benefit plan costs	1,303	1,249	(297)
Pension Benefits
Changes in Unamortized Benefit plan Costs (Table Amounts) [Abstract]
Change in net actuarial loss	2,353	2,687	(158)
Change in prior service cost	(2)	(608)
Amortization of:
Prior service credit	58	(23)	(48)
Net loss from previous years	(427)	(162)	(244)
Tax benefit related to above items	(788)	(752)	171
Change in unamortized benefit plan costs	1,194	1,142	(279)
Medical and Life Benefits
Changes in Unamortized Benefit plan Costs (Table Amounts) [Abstract]
Change in net actuarial loss	151	138	(64)
Change in prior service cost	0	6
Amortization of:
Prior service credit	51	51	60
Net loss from previous years	(21)	(17)	(26)
Tax benefit related to above items	(72)	(71)	12
Change in unamortized benefit plan costs	$ 109	$ 107	$ (18)