Fair Value Measurements (Fair Value of Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	Mar. 31, 2021	Mar. 31, 2020
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets at fair value	$ 3,490	$ 3,845
Total liabilities at fair value	59	50
Quoted Prices In Active Markets For Identical Financial Instruments (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets at fair value	2,712	2,293
Total liabilities at fair value	19	14
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets at fair value	778	1,552
Total liabilities at fair value	40	36
Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets at fair value	0	0
Total liabilities at fair value	0	0
Short-Term Investments [Member] | US Agencies Securities [Member] | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, Available-for-sale of securities	3
Short-Term Investments [Member] | Debt Security, Government, Non-US [Member] | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, Available-for-sale of securities	67
Short-Term Investments [Member] | Certificates of Deposit [Member] | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, Available-for-sale of securities	41
Short-Term Investments [Member] | Asset-backed Securities [Member] | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Instruments, Owned, Mortgages, Mortgage-backed and Asset-backed Securities, at Fair Value	112
Short-Term Investments [Member] | Significant Other Observable Inputs (Level 2) [Member] | US Agencies Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, Available-for-sale of securities	3	8
Short-Term Investments [Member] | Significant Other Observable Inputs (Level 2) [Member] | Debt Security, Government, Non-US [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, Available-for-sale of securities	67	42
Short-Term Investments [Member] | Significant Other Observable Inputs (Level 2) [Member] | Certificates of Deposit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, Available-for-sale of securities	41	56
Short-Term Investments [Member] | Significant Other Observable Inputs (Level 2) [Member] | Asset-backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Instruments, Owned, Mortgages, Mortgage-backed and Asset-backed Securities, at Fair Value	112	269
Short-Term Investments And Cash Equivalents [Member] | Corporate Bonds [Member] | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, Available-for-sale of securities	380	687
Short-Term Investments And Cash Equivalents [Member] | U.S. Treasury Securities [Member] | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, Available-for-sale of securities	437	603
Short-Term Investments And Cash Equivalents [Member] | US Agencies Securities [Member] | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, Available-for-sale of securities		8
Short-Term Investments And Cash Equivalents [Member] | Commercial Paper [Member] | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, Available-for-sale of securities	142	414
Short-Term Investments And Cash Equivalents [Member] | Debt Security, Government, Non-US [Member] | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, Available-for-sale of securities		42
Short-Term Investments And Cash Equivalents [Member] | Certificates of Deposit [Member] | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, Available-for-sale of securities		56
Short-Term Investments And Cash Equivalents [Member] | Asset-backed Securities [Member] | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Instruments, Owned, Mortgages, Mortgage-backed and Asset-backed Securities, at Fair Value		269
Short-Term Investments And Cash Equivalents [Member] | Quoted Prices In Active Markets For Identical Financial Instruments (Level 1) | U.S. Treasury Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, Available-for-sale of securities	437	603
Short-Term Investments And Cash Equivalents [Member] | Significant Other Observable Inputs (Level 2) [Member] | Corporate Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, Available-for-sale of securities	380	687
Short-Term Investments And Cash Equivalents [Member] | Significant Other Observable Inputs (Level 2) [Member] | Commercial Paper [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, Available-for-sale of securities	142	414
Cash Equivalents [Member] | Bank Time Deposits [Member] | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, Cash equivalents	157	78
Cash Equivalents [Member] | Money Market Funds [Member] | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, Cash equivalents	2,100	1,599
Cash Equivalents [Member] | Quoted Prices In Active Markets For Identical Financial Instruments (Level 1) | Bank Time Deposits [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, Cash equivalents	157	78
Cash Equivalents [Member] | Quoted Prices In Active Markets For Identical Financial Instruments (Level 1) | Money Market Funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, Cash equivalents	2,100	1,599
Other Current Assets and Other Assets [Domain] | Foreign Currency Derivatives [Member] | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, Foreign currency derivatives, assets	33	76
Other Current Assets and Other Assets [Domain] | Significant Other Observable Inputs (Level 2) [Member] | Foreign Currency Derivatives [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, Foreign currency derivatives, assets	33	76
Other Assets [Member] | Deferred compensation plan assets | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, Deferred compensation plan assets and liabilities	18	13
Other Assets [Member] | Quoted Prices In Active Markets For Identical Financial Instruments (Level 1) | Deferred compensation plan assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, Deferred compensation plan assets and liabilities	18	13
Accrued and Other Current Liabilities [Member] | Foreign Currency Derivatives [Member] | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, Foreign currency derivatives, liabilities	40	36
Accrued and Other Current Liabilities [Member] | Significant Other Observable Inputs (Level 2) [Member] | Foreign Currency Derivatives [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, Foreign currency derivatives, liabilities	40	36
Other Liabilities [Members] | Deferred Compensation Plan Liabilities [Member] | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, Deferred compensation plan assets and liabilities	19	14
Other Liabilities [Members] | Quoted Prices In Active Markets For Identical Financial Instruments (Level 1) | Deferred Compensation Plan Liabilities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, Deferred compensation plan assets and liabilities	$ 19	$ 14