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	$ 17	$ 15	$ 33	$ 30
Interest cost	39	38	78	77
Expected return on plan assets	42	42	83	84
Net actuarial loss	30	24	60	47
Prior service cost (credit)	0	1	0	2
Net transition liability			0	0
Settlements	0	2	2	2
Net periodic benefit cost	44	38	90	74
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	14	13	27	26
Interest cost	23	24	46	47
Expected return on plan assets	16	15	31	31
Net actuarial loss	14	10	28	21
Prior service cost (credit)	(4)	(4)	(8)	(8)
Net transition liability			1	1
Settlements	0	0	0	0
Net periodic benefit cost	$ 31	$ 28	$ 63	$ 56