Financing Arrangement (Carrying Values Of Liability And Equity Components Of Notes) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Mar. 31, 2012
Debt Instruments [Abstract]
Principal amount of Notes	$ 632.5	$ 632.5
Unamortized discount of the liability component	(79)	(94)
Net carrying amount of Notes	554	539	[1]
Equity component, net	$ 105	$ 105

[1] Derived from audited consolidated financial statements.