Retirement Benefits (Details 4) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Change in plan assets
Fair value of plan assets at beginning of year	$ 22,286
Employer contributions	300	1,000
Fair value of plan assets at end of year	24,024	22,286
Amounts Expected to be Recognized in 2013 Net Periodic Benefit Cost [Abstract]
Non-current liability	(6,085)	(4,079)
Pension Benefits
Change in projected benefit obligation
Projected benefit obligation at beginning of year	24,129	21,820
Service cost	522	520	531
Interest cost	1,184	1,223	1,212
Plan participants’ contributions	12	14
Plan amendments	(1)	(608)
Actuarial loss	3,114	2,379
Benefits paid	(1,220)	(1,197)
Other	6	(22)
Projected benefit obligation at end of year	27,746	24,129	21,820
Change in plan assets
Fair value of plan assets at beginning of year	21,340	20,081
Gain on plan assets	2,463	1,342
Employer contributions	366	1,084
Plan participants’ contributions	12	14
Benefits paid	(1,220)	(1,197)
Other	1	16
Fair value of plan assets at end of year	22,962	21,340	20,081
Funded status	(4,784)	(2,789)
Amounts Expected to be Recognized in 2013 Net Periodic Benefit Cost [Abstract]
Non-current assets	7	112
Current liability	(111)	(104)
Non-current liability	(4,680)	(2,797)
Medical and Life Benefits
Change in projected benefit obligation
Projected benefit obligation at beginning of year	2,235	2,104
Service cost	34	32	34
Interest cost	109	114	117
Plan participants’ contributions	81	82
Plan amendments	0	6
Actuarial loss	202	107
Benefits paid	(227)	(224)
Other	14	14
Projected benefit obligation at end of year	2,448	2,235	2,104
Change in plan assets
Fair value of plan assets at beginning of year	946	932
Gain on plan assets	119	31
Employer contributions	129	111
Plan participants’ contributions	81	82
Benefits paid	(227)	(224)
Other	14	14
Fair value of plan assets at end of year	1,062	946	932
Funded status	(1,386)	(1,289)
Amounts Expected to be Recognized in 2013 Net Periodic Benefit Cost [Abstract]
Non-current assets	49	41
Current liability	(30)	(48)
Non-current liability	$ (1,405)	$ (1,282)