Derivative Financial Instruments (Narrative) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Dec. 31, 2011 months	Dec. 31, 2011 Cash Flow Hedging [Member]	Mar. 31, 2011 Cash Flow Hedging [Member]	Dec. 31, 2011 Balance Sheet Hedging [Member]	Mar. 31, 2011 Balance Sheet Hedging [Member]	Dec. 31, 2011 Nondesignated [Member] Balance Sheet Hedging [Member]	Mar. 31, 2011 Nondesignated [Member] Balance Sheet Hedging [Member]	Dec. 31, 2011 Nondesignated [Member] British Pounds Sterling [Member] Balance Sheet Hedging [Member]	Mar. 31, 2011 Nondesignated [Member] British Pounds Sterling [Member] Balance Sheet Hedging [Member]
Derivative [Line Items]
Maturity period, maximum (in months)	15
Notional value of foreign currency purchase contracts		$ 90	$ 40			$ 30	$ 31
Notional value of foreign currency sale contracts		46	10			623	140	9	16
Notional value of foreign currency forward contracts				$ 662	$ 187