(Fair Value Of Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Mar. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Accrued Liabilities, Fair Value Disclosure	$ 102	$ 136
Quoted Prices In Active Markets For Identical Financial Instruments (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Total assets at fair value	1,939	3,032
Total liabilities at fair value	13	12
Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Total assets at fair value	1,519	765
Total liabilities at fair value	5	16
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	102	136
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		294
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		327
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		57
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		58
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	584
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	660
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	31
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	480	233
Short-Term Investments And Cash Equivalents | 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	48
Short-Term Investments And Cash Equivalents | Significant Other Observable Inputs (Level 2) | Asset-backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Asset-backed securities	242	55
Short-Term Investments And Cash Equivalents | 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	22
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	24	23
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	1,319	2,704
Cash Equivalents | 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		2
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	36	33
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	12	11
Accrued And Other Current Liabilities [Member] | Fair Value, Inputs, Level 3 [Member] | Contingent consideration
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Accrued Liabilities, Fair Value Disclosure	102
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	5	16
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	13	12
Other liabilities | Fair Value, Inputs, Level 3 [Member] | Contingent consideration
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Accrued Liabilities, Fair Value Disclosure	102	136
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Total assets at fair value	3,458	3,797
Total liabilities at fair value	120	164
Fair Value | Short-term investments | Corporate bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Available-for-sale of securities		327
Fair Value | Short-term investments | U.S. Treasury securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Available-for-sale of securities		294
Fair Value | Short-term investments | U.S. agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Available-for-sale of securities		57
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		58
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	660
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	584
Fair Value | Short-Term Investments And Cash Equivalents | U.S. agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Available-for-sale of securities	31
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	480	233
Fair Value | Short-Term Investments And Cash Equivalents | Debt Security, Government, Non-US [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Available-for-sale of securities	48
Fair Value | Short-Term Investments And Cash Equivalents | Asset-backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Asset-backed securities	242	55
Fair Value | Short-Term Investments And Cash Equivalents | Certificates of Deposit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Available-for-sale of securities	22
Fair Value | Cash Equivalents | Bank Time Deposits [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Cash equivalents	24	23
Fair Value | Cash Equivalents | Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Cash equivalents	1,319	2,704
Fair Value | Cash Equivalents | Certificates of Deposit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Available-for-sale of securities		2
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	36	33
Fair Value | Other assets | Deferred compensation plan assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Deferred compensation plan assets	12	11
Fair Value | Accrued And Other Current Liabilities [Member] | Contingent consideration
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Accrued Liabilities, Fair Value Disclosure	102
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	5	16
Fair Value | Other liabilities | Contingent consideration
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Accrued Liabilities, Fair Value Disclosure		136
Fair Value | Other liabilities | Deferred Compensation Plan Liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value, Deferred compensation plan assets	$ 13	$ 12