Credit Facilities (Details) - USD ($) $ in Millions |
6 Months Ended | 12 Months Ended |
|---|---|---|
Mar. 31, 2019 |
Sep. 30, 2018 |
|
| Revolving Credit Facility [Member] | ||
| Line of Credit Facility [Abstract] | ||
| Credit Facility, Maximum Borrowing Capacity | $ 5,000 | |
| Line of Credit Facility, Interest Rate Description | Loans under the Revolving Credit Facility will bear interest, at our option, at either the reserve-adjusted Eurocurrency Rate (determined in accordance with the Revolving Credit Facility) or the Base Rate (determined in accordance with the Revolving Credit Facility), in each case plus an applicable margin based on our long-term unsecured senior, non-credit enhanced debt ratings. The margins over the reserve-adjusted Eurocurrency Rate and the Base Rate will be 0.805% and 0.00% per annum, respectively. | |
| Debt Instrument, Ticking Fee | The Revolving Credit Facility has a facility fee, which accrues at a rate of 0.07% per annum. | |
| Line of Credit Facility, Covenant Terms | maintain a ratio of consolidated earnings before interest, taxes, depreciation and amortization to consolidated interest expense, as defined in each of the respective agreements, of not less than three to one at the end of each fiscal quarter | |
| Line of Credit Facility, Covenant Compliance | we were in compliance with the applicable covenants | |
| Revolving Credit Facility [Member] | February 2020 [Member] | ||
| Line of Credit Facility [Abstract] | ||
| Credit Facility, Maximum Borrowing Capacity | $ 530 | |
| Credit Facility, Expiration Date | Feb. 18, 2020 | |
| Revolving Credit Facility [Member] | November 2021 [Member] | ||
| Line of Credit Facility [Abstract] | ||
| Credit Facility, Maximum Borrowing Capacity | $ 4,470 | |
| Credit Facility, Expiration Date | Nov. 08, 2021 | |
| Commercial Paper [Member] | ||
| Line of Credit Facility [Abstract] | ||
| Credit Facility, Maximum Borrowing Capacity | $ 5,000 | |
| Outstanding Commercial Paper Classified as Short-term debt | $ 1,000 | $ 1,000 |
| Commercial Paper, Weighted Average Interest Rate | 2.74% | 2.35% |
| Commercial Paper [Member] | Minimum [Member] | ||
| Line of Credit Facility [Abstract] | ||
| Debt Instrument, Term | 1 day | |
| Commercial Paper [Member] | Maximum [Member] | ||
| Line of Credit Facility [Abstract] | ||
| Debt Instrument, Term | 397 days | |
| Commercial Paper [Member] | Weighted Average [Member] | ||
| Line of Credit Facility [Abstract] | ||
| Commercial Paper, Weighted Average Remaining Term | 29 days | 16 days |