Other Commitments And Contingent Liabilities (Litigation Reserve And Expense) (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	3 Months Ended					12 Months Ended
	Apr. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2010	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2010
Loss Contingencies [Line Items]
Payments made							$ (26)	$ (26)	$ (350)
Average Wholesale Price Litigation [Member]
Loss Contingencies [Line Items]
AWP litigation reserve at beginning of period	453						330	143	143
Charges incurred		4	27	118	189	24	149	213	0
Payments made	(191)						(26)	(26)	0
AWP litigation reserve at end of period		$ 453					$ 453	$ 330	$ 143