Retirement Benefits and Trusteed Assets (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 15	$ 11	$ 48	$ 41
Interest cost	38	39	116	116
Expected return on plan assets	(41)	(42)	(124)	(126)
Net actuarial loss	33	27	93	74
Prior service cost (credit)	0	1	0	3
Net transition liability			0	0
Settlements	0	0	2	2
Net periodic benefit cost	45	36	135	110
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	11	11	38	37
Interest cost	23	21	69	68
Expected return on plan assets	(15)	(16)	(46)	(47)
Net actuarial loss	16	9	44	30
Prior service cost (credit)	(4)	(4)	(12)	(12)
Net transition liability			1	2
Settlements	0	1	0	0
Net periodic benefit cost	$ 31	$ 22	$ 94	$ 78