(Fair Value Of Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions		Sep. 30, 2017	Mar. 31, 2017
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Total assets at fair value		$ 2,815	$ 2,778
Total liabilities at fair value		58	17
Quoted Prices In Active Markets For Identical Financial Instruments (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Total assets at fair value		860	1,106
Total liabilities at fair value		10	9
Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Total assets at fair value		1,955	1,672
Total liabilities at fair value		48	8
Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Total assets at fair value		0	0
Total liabilities at fair value		0	0
Short-term investments | Significant Other Observable Inputs (Level 2) | Foreign Government Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Available-for-sale of securities		101	113
Short-term investments | Significant Other Observable Inputs (Level 2) | Asset-backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Asset-backed securities		119	135
Short-term investments | Significant Other Observable Inputs (Level 2) | Certificates of Deposit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Available-for-sale of securities		26
Short-Term Investments And Cash Equivalents | Quoted Prices In Active Markets For Identical Financial Instruments (Level 1) | U.S. Treasury securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Available-for-sale of securities		453	460
Short-Term Investments And Cash Equivalents | Significant Other Observable Inputs (Level 2) | Corporate bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Available-for-sale of securities		1,247	963
Short-Term Investments And Cash Equivalents | Significant Other Observable Inputs (Level 2) | U.S. agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Available-for-sale of securities		133	172
Short-Term Investments And Cash Equivalents | Significant Other Observable Inputs (Level 2) | Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Available-for-sale of securities		320	270
Cash Equivalents | Quoted Prices In Active Markets For Identical Financial Instruments (Level 1) | Bank Time Deposits [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Cash equivalents		304	233
Cash Equivalents | Quoted Prices In Active Markets For Identical Financial Instruments (Level 1) | Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Cash equivalents		93	405
Other Current Assets and Other Assets [Domain] | Significant Other Observable Inputs (Level 2) | Foreign currency derivatives
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Foreign currency derivatives, assets		9	19
Other assets | Quoted Prices In Active Markets For Identical Financial Instruments (Level 1) | Deferred compensation plan assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Deferred compensation plan assets	[1]	10	8
Accrued and Other Current Liabilities and Other Liabilities | Significant Other Observable Inputs (Level 2) | Foreign currency derivatives
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Foreign currency derivatives, liabilities		48	8
Other liabilities | Quoted Prices In Active Markets For Identical Financial Instruments (Level 1) | Deferred Compensation Plan Liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Deferred compensation plan assets	[1]	$ 10	$ 9

[1] The Deferred Compensation Plan assets consist of various mutual funds. See Note 13 in our Annual Report on Form 10-K for the fiscal year ended March 31, 2017, for additional information regarding our Deferred Compensation Plan.