Commitments And Contingencies (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Loss Contingencies [Line Items]
Amount of potential cash payments that could result from unrecognized tax benefits	$ 104
Operating Leases, Rent Expense	91	$ 89	$ 97
Maximum [Member] | Unrecorded Unconditional Purchase Obligations Payable in Common Stock Per Year [Member]
Loss Contingencies [Line Items]
Unrecorded Unconditional Purchase Obligation	10
Maximum [Member] | Unrecorded Unconditional Purchase Obligation Payable in Common Stock [Member]
Loss Contingencies [Line Items]
Unrecorded Unconditional Purchase Obligation	$ 32