Retirement Benefits (Details 4) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Change in plan assets
Fair value of plan assets at end of year	$ 25,273	$ 24,024
Amounts Recognized on the Balance Sheet
Non-current liability	(2,954)	(6,085)
Pension Benefits
Change in projected benefit obligation
Projected benefit obligation at beginning of year	27,746	24,129
Service cost	516	522	520
Interest cost	1,117	1,184	1,223
Plan participants’ contributions	12	12
Plan amendments	0	(1)	640
Actuarial (gain) loss	(2,063)	3,114
Benefits paid	(1,365)	(1,220)
Other	9	6
Projected benefit obligation at end of year	25,972	27,746	24,129
Change in plan assets
Fair value of plan assets at beginning of year	22,962	21,340
Gain on plan assets	1,907	2,463
Employer contributions	579	366
Plan participants’ contributions	12	12
Benefits paid	(1,365)	(1,220)
Other	3	1
Fair value of plan assets at end of year	24,098	22,962	21,340
Funded status	(1,874)	(4,784)
Amounts Recognized on the Balance Sheet
Non-current assets	117	7
Current liability	(122)	(111)
Non-current liability	(1,869)	(4,680)
Medical and Life Benefits
Change in projected benefit obligation
Projected benefit obligation at beginning of year	2,448	2,235
Service cost	36	34	32
Interest cost	96	109	114
Plan participants’ contributions	77	81
Plan amendments	0	0
Actuarial (gain) loss	(219)	202
Benefits paid	(227)	(227)
Other	13	14
Projected benefit obligation at end of year	2,224	2,448	2,235
Change in plan assets
Fair value of plan assets at beginning of year	1,062	946
Gain on plan assets	137	119
Employer contributions	114	129
Plan participants’ contributions	77	81
Benefits paid	(227)	(227)
Other	12	14
Fair value of plan assets at end of year	1,175	1,062	946
Funded status	(1,049)	(1,386)
Amounts Recognized on the Balance Sheet
Non-current assets	72	49
Current liability	(36)	(30)
Non-current liability	$ (1,085)	$ (1,405)