Retirement Benefits and Trusteed Assets Retirement Benefits and Trusted Assets (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Service Cost	$ 19	$ 16
Defined Benefit Plan, Interest Cost	36	39
Defined Benefit Plan, Expected Return on Plan Assets	(46)	(41)
Defined Benefit Plan, Amortization of Net Gains (Losses)	36	30
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	0	0
Defined Benefit Plan Net Transition Liability	0	0
Defined Benefit Plan, Special Termination Benefits	0	2
Defined Benefit Plan, Net Periodic Benefit Cost	45	46
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Service Cost	12	13
Defined Benefit Plan, Interest Cost	18	23
Defined Benefit Plan, Expected Return on Plan Assets	(18)	(15)
Defined Benefit Plan, Amortization of Net Gains (Losses)	12	14
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	(17)	(4)
Defined Benefit Plan Net Transition Liability	0	1
Defined Benefit Plan, Special Termination Benefits	0	0
Defined Benefit Plan, Net Periodic Benefit Cost	$ 7	$ 32