Fair Value Measurements (Fair Value Measurements Using Significant Unobservable Inputs (Level 3)) (Details) (Significant Unobservable Inputs (Level 3) [Member], Contingent Consideration [Member], USD $) In Millions	6 Months Ended	12 Months Ended
	Sep. 30, 2011	Mar. 31, 2011
Significant Unobservable Inputs (Level 3) [Member] | Contingent Consideration [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning Balance	$ 51	$ 65
Additions	97	3
Change in fair value	18	(17)	[1]
Ending Balance	$ 166	$ 51

[1] The change in fair value is reported as acquisition-related contingent consideration in our Condensed Consolidated Statements of Operations.