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	$ 20	$ 15	$ 61	$ 52
Interest cost	51	51	153	152
Expected return on plan assets	(61)	(62)	(183)	(185)
Net actuarial loss	48	41	133	107
Prior service cost (credit)	0	0	0	2
Net transition liability	0	0	0	0
Settlements			2	2
Net periodic benefit cost	58	45	166	130
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	15	14	51	48
Interest cost	29	28	90	90
Expected return on plan assets	(23)	(24)	(69)	(71)
Net actuarial loss	21	12	60	42
Prior service cost (credit)	(6)	(7)	(20)	(20)
Net transition liability	0	1	1	2
Settlements			0	0
Net periodic benefit cost	$ 36	$ 24	$ 113	$ 91