Revenues - Disaggregation of Revenue (Details) - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Sep. 30, 2019 |
Sep. 30, 2018 |
Sep. 30, 2017 |
|
| Disaggregation of Revenue [Line Items] | |||
| Net revenues | $ 22,977 | $ 20,609 | $ 18,358 |
| U.S. | |||
| Disaggregation of Revenue [Line Items] | |||
| Net revenues | 10,279 | 9,332 | 8,704 |
| International | |||
| Disaggregation of Revenue [Line Items] | |||
| Net revenues | 12,698 | 11,277 | 9,654 |
| Service revenues | |||
| Disaggregation of Revenue [Line Items] | |||
| Net revenues | 9,700 | 8,918 | 7,975 |
| Data processing revenues | |||
| Disaggregation of Revenue [Line Items] | |||
| Net revenues | 10,333 | 9,027 | 7,786 |
| International transaction revenues | |||
| Disaggregation of Revenue [Line Items] | |||
| Net revenues | 7,804 | 7,211 | 6,321 |
| Other revenues | |||
| Disaggregation of Revenue [Line Items] | |||
| Net revenues | 1,313 | 944 | 841 |
| Client incentives | |||
| Disaggregation of Revenue [Line Items] | |||
| Net revenues | $ (6,173) | $ (5,491) | $ (4,565) |