Retirement Benefits and Trusteed Assets (Details) (Pension Plans, Defined Benefit [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 64	$ 55	$ 52
Interest cost	155	154	153
Expected return on plan assets	(166)	(168)	(171)
Amortization of: [Abstract]
Net actuarial loss	124	99	70
Prior service cost	1	4	5
Settlements	2	2	0
Net pension cost	$ 180	$ 146	$ 109