Description Of Business And Summary Of Significant Accounting Policies (Foreign Currency Translation) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Mar. 31, 2013
Derivative [Line Items]      
Net gain (loss) on foreign currency forward contracts $ 59 $ (5) $ (2)
Foreign Currency Transaction Gain (Loss), Realized (62) 4 2
Interest And Other Income Expense Net [Member]      
Derivative [Line Items]      
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net $ 58 $ (5) $ (2)