Benefit Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Pension Plans [Member]
Components of Net Periodic Benefit Cost
Service Cost	$ 19	$ 18
Interest Cost	56	59
Expected Return on Plan Assets	(80)	(79)
Amortization of Prior Service Credit	0	0
Amortization of Net Actuarial Loss	37	30
Net Periodic Benefit Cost	32	28
Other Postretirement Benefit Plans [Member]
Components of Net Periodic Benefit Cost
Service Cost	12	11
Interest Cost	26	27
Expected Return on Plan Assets	(25)	(27)
Amortization of Prior Service Credit	(5)	0
Amortization of Net Actuarial Loss	14	7
Net Periodic Benefit Cost	$ 22	$ 18