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Debt and Financing Activities - Long-Term Debt Narrative (Details) - USD ($) | Dec. 03, 2020 | Dec. 31, 2020 | Dec. 01, 2020 | Mar. 31, 2020
--- | --- | --- | --- | ---
Debt Instrument [Line Items] |  |  |  |
Long-term debt |  | $ 7,244,000,000 |  | $ 7,387,000,000
Current portion of long-term debt |  | $ 777,000,000 |  | $ 1,052,000,000
0.90% Notes due December 3, 2025 | Term Loan |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate on debt instrument (percent) | 0.90% | 0.90% |  |
Debt principal amount | $ 500,000,000 |  |  |
Proceeds from debt issuance | $ 496,000,000 |  |  |
Price as percentage of debt outstanding at which debt can be purchased | 101.00% |  |  |
3.65% Notes due November 30, 2020 | Term Loan |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate on debt instrument (percent) |  | 3.65% |  |
Debt principal amount |  | $ 700,000,000 |  |
4.75% Notes due March 1, 2021 | Term Loan |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Interest rate on debt instrument (percent) |  | 4.75% | 4.75% |
Debt principal amount |  |  | $ 323,000,000 |

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