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Equity - Narrative (Details) - USD ($) shares in Millions, $ in Millions |  | 1 Months Ended | 3 Months Ended | 6 Months Ended | 9 Months Ended |
--- | --- | --- | --- | --- | --- | ---
Oct. 29, 2018 | Apr. 30, 2019 | Jun. 30, 2019 | Jun. 30, 2018 | Jun. 30, 2019 | Jun. 30, 2018 | Jun. 30, 2019 | Oct. 25, 2018
Accelerated Share Repurchases [Line Items] |  |  |  |  |  |  |  |
Treasury stock shares acquired |  |  | $ 1,235 | $ 1,596 | $ 2,325 | $ 2,162 |  |
Accelerated Share Repurchase Agreement |  |  |  |  |  |  |  |
Accelerated Share Repurchases [Line Items] |  |  |  |  |  |  |  |
Share repurchase program authorized amount |  |  |  |  |  |  |  | $ 5,000
Treasury stock shares purchased (in shares) | 56.7 | 7.7 |  |  |  |  | 64.4 |
Payment under ASR agreement | $ 5,000 |  |  |  |  |  |  |
Treasury stock shares acquired | 4,000 |  |  |  |  |  |  |
Decrease in other-paid-in capital | $ 1,000 |  |  |  |  |  |  |

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