Derivative Financial Instruments (Narrative) (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Sep. 30, 2013	Sep. 30, 2013 Not designated as hedging instrument	Mar. 31, 2013 Not designated as hedging instrument	Sep. 30, 2013 Foreign currency contracts to purchase Not designated as hedging instrument United States Dollar	Mar. 31, 2013 Foreign currency contracts to purchase Not designated as hedging instrument United States Dollar	Sep. 30, 2013 Foreign currency contracts to sell Not designated as hedging instrument British Pounds Sterling	Mar. 31, 2013 Foreign currency contracts to sell Not designated as hedging instrument British Pounds Sterling	Sep. 30, 2013 Foreign currency contracts to sell Not designated as hedging instrument United States Dollar	Mar. 31, 2013 Foreign currency contracts to sell Not designated as hedging instrument United States Dollar
Derivative
Maturity period of foreign currency forward and option contracts, Maximum	12 months
Maturity period of foreign currency forward contracts, Maximum	3 months
Derivative, Notional amount		$ 337	$ 306	$ 33	$ 87	$ 3	$ 6	$ 301	$ 213