(Fair Value Of Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Mar. 31, 2020
Quoted Prices In Active Markets For Identical Financial Instruments (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Total assets at fair value	$ 3,025	$ 2,293
Total liabilities at fair value	18	14
Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Total assets at fair value	1,480	1,552
Total liabilities at fair value	72	36
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) | U.S. agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Available-for-sale of securities	4	8
Short-term investments | Significant Other Observable Inputs (Level 2) | Debt Security, Government, Non-US [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Available-for-sale of securities	72	42
Short-term investments | Significant Other Observable Inputs (Level 2) | Asset-backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Asset-backed securities	209	269
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	80	56
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	570	603
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	686	687
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	407	414
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	136	78
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	2,301	1,599
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	22	76
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	18	13
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	72	36
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	18	14
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Total assets at fair value	4,505	3,845
Total liabilities at fair value	90	50
Fair Value | Short-term investments | U.S. agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Available-for-sale of securities	4	8
Fair Value | Short-term investments | Debt Security, Government, Non-US [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Available-for-sale of securities	72	42
Fair Value | Short-term investments | Asset-backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Asset-backed securities	209	269
Fair Value | Short-term investments | Certificates of Deposit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Available-for-sale of securities	80	56
Fair Value | Short-Term Investments And Cash Equivalents | Corporate bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Available-for-sale of securities	686	687
Fair Value | Short-Term Investments And Cash Equivalents | U.S. Treasury securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Available-for-sale of securities	570	603
Fair Value | Short-Term Investments And Cash Equivalents | Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Available-for-sale of securities	407	414
Fair Value | Cash Equivalents | Bank Time Deposits [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Cash equivalents	136	78
Fair Value | Cash Equivalents | Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Cash equivalents	2,301	1,599
Fair Value | Other Current Assets and Other Assets [Domain] | Foreign currency derivatives
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Foreign currency derivatives, assets	22	76
Fair Value | Other assets | Deferred compensation plan assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Deferred compensation plan assets	18	13
Fair Value | Accrued and Other Current Liabilities and Other Liabilities | Foreign currency derivatives
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Foreign currency derivatives, liabilities	72	36
Fair Value | Other liabilities | Deferred Compensation Plan Liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Deferred compensation plan assets	$ 18	$ 14