Commitments And Contingencies (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Loss Contingencies [Line Items]
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High	$ 140
Business Combination, Contingent Consideration, Liability	122
Income tax obligations	205
Operating Leases, Rent Expense	92	$ 91	$ 89
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