Retirement Benefits and Trusteed Assets (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 20	$ 18	$ 41	$ 37
Interest cost	51	50	102	101
Expected return on plan assets	(61)	(61)	122	123
Net actuarial loss	43	33	85	66
Prior service cost (credit)	0	1	0	2
Net transition liability			0	0
Settlements	0	2	(2)	(2)
Net periodic benefit cost	53	43	108	85
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	18	17	36	34
Interest cost	31	31	61	62
Expected return on plan assets	(23)	(23)	46	47
Net actuarial loss	20	15	39	30
Prior service cost (credit)	(7)	(6)	(14)	(13)
Net transition liability			1	1
Settlements	0	0	0	0
Net periodic benefit cost	$ 39	$ 34	$ 77	$ 67