Retirement Benefits (Details 4) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Change in Projected Benefit Obligation [Abstract]
Actuarial loss (gain)	$ 3,900	$ 2,800
Change in Plan Assets
Fair value of plan assets at beginning of year	21,013
Fair value of plan assets at end of year	22,286	21,013
Pension Benefits
Change in Projected Benefit Obligation [Abstract]
Projected benefit obligation at beginning of year	21,820	20,661
Service cost	520	531	547
Interest cost	1,223	1,212	1,180
Plan participants' contributions	14	10
Plan amendments	(608)
Actuarial loss (gain)	2,379	633
Benefits paid	(1,197)	(1,176)
Other	(22)	(51)
Projected benefit obligation at end of year	24,129	21,820	20,661
Change in Plan Assets
Fair value of plan assets at beginning of year	20,081	18,184
Gain on plan assets	1,342	2,320
Employer contributions	1,084	789
Plan participants' contributions	14	10
Benefits paid	(1,197)	(1,176)
Other	16	(46)
Fair value of plan assets at end of year	21,340	20,081	18,184
Funded status	(2,789)	(1,739)
Medical and Life Benefits
Change in Projected Benefit Obligation [Abstract]
Projected benefit obligation at beginning of year	2,104	2,104
Service cost	32	34	34
Interest cost	114	117	124
Plan participants' contributions	82	82
Plan amendments	6
Actuarial loss (gain)	107	(27)
Benefits paid	(224)	(222)
Other	14	16
Projected benefit obligation at end of year	2,235	2,104	2,104
Change in Plan Assets
Fair value of plan assets at beginning of year	932	843
Gain on plan assets	31	108
Employer contributions	111	105
Plan participants' contributions	82	82
Benefits paid	(224)	(222)
Other	14	16
Fair value of plan assets at end of year	946	932	843
Funded status	$ (1,289)	$ (1,172)