Retirement Benefits and Trusteed Assets (Details 2) (USD $) In Millions, unless otherwise specified	1 Months Ended		12 Months Ended
	Jan. 31, 2012	Jan. 31, 2011	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Regulatory Assets			$ 4,853	$ 4,158
Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Accumulated benefit obligation, end of year			3,881	3,521
Benefit obligation, beginning of year	4,195	3,785	3,785	3,436
Consolidation of VIEs			0	82
Service cost			69	64	52
Interest cost			202	202	203
Actuarial loss			355	216
Special termination benefits			2	0	0
Benefits paid			(218)	(215)
Benefit obligation, end of year			4,195	3,785	3,436
Plan assets at fair value, beginning of the yeard Benefit Plan, Fair Value of Plan Assets	2,886	2,913	2,913	2,549
Consolidation of VIEs			0	64
Actual return on plan assets			(18)	309
Company contributions	240	200	209	206
Plan assets at fair value, end of the yeard Benefit Plan, Fair Value of Plan Assets			2,886	2,913	2,549
Funded status of the plans			(1,309)	(872)
Current liabilities			(11)	(6)
Noncurrent liabilities			(1,298)	(866)
Pension and Other Postretirement Defined Benefit Plans, Liabilities			(1,309)	(872)
Net actuarial loss			202	195
Prior serice cost (credit)			(3)	(4)
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), before Tax			199	191
Net actuarial loss			2,201	1,730
Prior service cost			7	12
Regulatory Assets			$ 2,208	$ 1,742