Retirement Benefits (Unaudited) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Defined Contribution Pension and Other Postretirement Plans Disclosure [Abstract]
Defined contribution plan, employer contributions	$ 74	$ 75	$ 147	$ 150
Pension Benefits
Components of Net Periodic Benefit Cost
Service cost	115	129	229	258
Interest cost	315	280	630	559
Expected return on plan assets	(468)	(452)	(935)	(905)
Amortization of:
Prior service cost (credit)	(15)	(15)	(30)	(29)
Net loss from previous years	82	152	164	304
Net periodic benefit cost	29	94	58	187
Employer Contributions
Defined benefit plan, employer contributions			39
Medical and Life Benefits
Components of Net Periodic Benefit Cost
Service cost	9	9	17	18
Interest cost	24	24	50	48
Expected return on plan assets	(21)	(19)	(42)	(38)
Amortization of:
Prior service cost (credit)	(13)	(13)	(20)	(25)
Net loss from previous years	4	8	6	15
Net periodic benefit cost	3	9	11	18
Employer Contributions
Defined benefit plan, employer contributions			$ 26