Fair Value Of Financial Assets And Liabilities (Additional Fair Value Disclosure) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2012		Dec. 31, 2011
Book Value [Member]
Long-term debt, including current maturities	$ 20,093	[1]	$ 20,573	[1]
Fair Value [Member]
Long-term debt, including current maturities	22,332		23,053
Variable Interest Entity [Member]
Debt of variable interest entities	$ 945		$ 949

[1] Includes Non-recourse long-term debt of variable interest entities of $945 million and $949 million at March 31, 2012 and December 31, 2011, respectively.