Retirement Benefits (Unaudited) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Defined Contribution Pension and Other Postretirement Plans Disclosure [Abstract]
Defined contribution plan, employer contributions	$ 63	$ 66	$ 213	$ 218
Pension Benefits
Components of Net Periodic Benefit Cost
Service cost	129	131	387	392
Interest cost	279	296	838	888
Expected return on plan assets	(452)	(427)	(1,357)	(1,281)
Amortization of:
Prior service cost (credit)	(15)	(15)	(44)	(44)
Net loss from previous years	152	107	456	321
Defined Benefit Plan, Other Costs	0	0	0	2
Net periodic benefit cost	93	92	280	278
Employer Contributions
Defined benefit plan, employer contributions			561
Pension Benefits | Voluntary Contributions [Member]
Employer Contributions
Defined benefit plan, employer contributions			500
Medical and Life Benefits
Components of Net Periodic Benefit Cost
Service cost	9	8	27	25
Interest cost	24	28	72	82
Expected return on plan assets	(19)	(17)	(57)	(51)
Amortization of:
Prior service cost (credit)	(13)	(13)	(38)	(38)
Net loss from previous years	8	5	23	15
Defined Benefit Plan, Other Costs	0	0	0	0
Net periodic benefit cost	9	11	27	33
Employer Contributions
Defined benefit plan, employer contributions			87
Pension Employer Required Minimum Contribution
Employer Contributions
Defined benefit plan, expected contributions in current fiscal year			66
OPEB Employer Required Minimum Contribution
Employer Contributions
Defined benefit plan, expected contributions in current fiscal year			$ 110