Other Postretirement Benefits (Net Periodic Postretirement Benefit Costs) (Details) (Other Postretirement Benefits [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Other Postretirement Benefits [Member]
Schedule Of Other Postretirement Benefits [Line Items]
Service cost	$ 7	$ 6
Interest cost on accumulated other postretirement benefit obligation	18	21
Expected return on plan assets	(21)	(22)
Amortization of net actuarial loss	25	22
Amortization of prior service costs	(5)	(2)
Amortization of transition obligation		1
NET PERIODIC POSTRETIREMENT BENEFIT COST	24	26
Cost capitalized	(8)	(9)
Cost charged	7	4
Cost charged to operating expenses	23	21
Expected contributions	$ 87