(Fair Value Of Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions		Sep. 30, 2016	Mar. 31, 2016
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Total assets at fair value		$ 2,023	$ 1,915
Total liabilities at fair value		21	19
Quoted Prices In Active Markets For Identical Financial Instruments (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Total assets at fair value		809	903
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		1,214	1,012
Total liabilities at fair value		11	10
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 | 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		379
Short-term investments | Significant Other Observable Inputs (Level 2) | Corporate bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Available-for-sale of securities		739
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		115
Short-term investments | Significant Other Observable Inputs (Level 2) | Asset-backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Asset-backed securities		54
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			407
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			623
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		163	170
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		110	81
Short-Term Investments And Cash Equivalents | 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			122
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		236	345
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		185	143
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		33	16
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]	9	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		11	10
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 15 in our Annual Report on Form 10-K for the fiscal year ended March 31, 2016, for additional information regarding our Deferred Compensation Plan.