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Debt (Schedule Of Outstanding Debt) (Details) - USD ($) $ in Millions | Dec. 31, 2018 | Mar. 31, 2018 | Dec. 31, 2017
--- | --- | --- | ---
Debt Instrument [Line Items] |  |  |
Current portion of long-term debt | $ 314 |  | $ 262
Short-term debt | 314 |  | 262
Long-term debt, current and noncurrent | 5,824 |  | 5,487
Long-term debt and capital lease obligations | 5,510 |  | 5,225
2.55% Senior Debt Obligations Due 2018 |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt, current and noncurrent | $ 0 |  | 250
Interest rate | 2.55% |  |
2.35% Senior Debt Obligations Due 2019 |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt, current and noncurrent | $ 300 |  | 299
Interest rate | 2.35% |  |
2.35% Senior Debt Obligations Due 2020 |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt, current and noncurrent | $ 499 |  | 498
Interest rate | 2.35% |  |
4.80% Senior Debt Obligations Due 2021 |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt, current and noncurrent | $ 499 |  | 498
Interest rate | 4.80% |  |
2.75% Senior Debt Obligations Due 2022 |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt, current and noncurrent | $ 497 |  | 496
Interest rate | 2.75% |  |
3.30% Senior Debt Obligations Due 2023 |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt, current and noncurrent | $ 348 |  | 348
Interest rate | 3.30% |  |
4.05% Senior Debt Obligations Due 2023 |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt, current and noncurrent | $ 249 |  | 248
Interest rate | 4.05% |  |
3.50% Senior Debt Obligations Due 2024 |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt, current and noncurrent | $ 597 |  | 596
Interest rate | 3.50% |  |
3.50% Senior Debt Obligations Due 2025 |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt, current and noncurrent | $ 496 |  | 496
Interest rate | 3.50% |  |
3.75% Senior Debt Obligations Due 2026 |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt, current and noncurrent | $ 596 |  | 596
Interest rate | 3.75% |  |
5.875% Senior Debt Obligations Due 2033 |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt, current and noncurrent | $ 297 |  | 297
Interest rate | 5.875% |  |
4.35% Senior Debt Obligation Due 2047 |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt, current and noncurrent | $ 492 |  | 492
Interest rate | 4.35% |  |
4.20% Senior Debt Obligations Due 2048 |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt, current and noncurrent | $ 592 |  | 0
Interest rate | 4.20% | 4.20% |
Mortgage Due 2035 |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt, current and noncurrent | $ 358 |  | 370
Interest rate | 5.70% |  |
Other Debt Instruments |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt, current and noncurrent | $ 4 |  | $ 3

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