Retirement Benefits (Details 2) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Changes in Unamortized Benefit plan Costs (Table Amounts) [Abstract]
Change in net actuarial loss	$ 4,067	$ (2,438)	$ 2,504
Change in prior service cost	(92)		(2)
Amortization of:
Prior service credit	104	109	109
Net loss from previous years	(340)	(638)	(448)
Tax expense (benefit) related to above items	(1,423)	1,177	(860)
Change in unamortized benefit plan costs	2,316	(1,790)	1,303
Pension Benefits
Changes in Unamortized Benefit plan Costs (Table Amounts) [Abstract]
Change in net actuarial loss	3,833	(2,158)	2,353
Change in prior service cost	0		(2)
Amortization of:
Prior service credit	59	58	58
Net loss from previous years	(327)	(608)	(427)
Tax expense (benefit) related to above items	(1,357)	1,075	(788)
Change in unamortized benefit plan costs	2,208	(1,633)	1,194
Medical and Life Benefits
Changes in Unamortized Benefit plan Costs (Table Amounts) [Abstract]
Change in net actuarial loss	234	(280)	151
Change in prior service cost	(92)		0
Amortization of:
Prior service credit	45	51	51
Net loss from previous years	(13)	(30)	(21)
Tax expense (benefit) related to above items	(66)	102	(72)
Change in unamortized benefit plan costs	$ 108	$ (157)	$ 109