| **Segment Information - Net Revenue From External Customers and Intercompany Revenue From Each Operating Segment (Details) - USD ($) $ in Millions** | 3 Months Ended | 6 Months Ended |
|------------------------------------------------------------------------------------------------------------------------------------------------------|----------------|----------------|
||
| **Segment Reporting Information [Line Items]**                                                                                                       |           |           |   |   |
| Net revenue                                                                                                                                          | $ 768.5        | $ 582.5        | $ 1,328.0 | $ 946.6 |
| Live and Historical                                                                                                                                  |           |           |   |   |
| **Segment Reporting Information [Line Items]**                                                                                                       |           |           |   |   |
| Net revenue                                                                                                                                          | 408.0          | 275.9          | 623.8 | 363.1 |
| TwinSpires                                                                                                                                           |           |           |   |   |
| **Segment Reporting Information [Line Items]**                                                                                                       |           |           |   |   |
| Net revenue                                                                                                                                          | 139.1          | 138.5          | 235.5 | 239.9 |
| Gaming                                                                                                                                               |           |           |   |   |
| **Segment Reporting Information [Line Items]**                                                                                                       |           |           |   |   |
| Net revenue                                                                                                                                          | 247.9          | 184.5          | 499.5 | 363.7 |
| External Customer                                                                                                                                    |           |           |   |   |
| **Segment Reporting Information [Line Items]**                                                                                                       |           |           |   |   |
| Net revenue                                                                                                                                          | 768.5          | 582.5          | 1,328.0 | 946.6 |
| Operating Segments | Live and Historical                                                                                                             |           |           |   |   |
| **Segment Reporting Information [Line Items]**                                                                                                       |           |           |   |   |
| Net revenue                                                                                                                                          | 385.0          | 260.9          | 599.4 | 346.9 |
| Operating Segments | TwinSpires                                                                                                                      |           |           |   |   |
| **Segment Reporting Information [Line Items]**                                                                                                       |           |           |   |   |
| Net revenue                                                                                                                                          | 137.4          | 136.8          | 232.2 | 237.1 |
| Operating Segments | Gaming                                                                                                                          |           |           |   |   |
| **Segment Reporting Information [Line Items]**                                                                                                       |           |           |   |   |
| Net revenue                                                                                                                                          | 245.9          | 184.3          | 495.9 | 361.6 |
| Operating Segments | External Customer                                                                                                               |           |           |   |   |
| **Segment Reporting Information [Line Items]**                                                                                                       |           |           |   |   |
| Net revenue                                                                                                                                          | 768.3          | 582.0          | 1,327.5 | 945.6 |
| Operating Segments | External Customer | Live and Historical                                                                                         |           |           |   |   |
| **Segment Reporting Information [Line Items]**                                                                                                       |           |           |   |   |
| Net revenue                                                                                                                                          | 385.0          | 260.9          | 599.4 | 346.9 |
| Operating Segments | External Customer | TwinSpires                                                                                                  |           |           |   |   |
| **Segment Reporting Information [Line Items]**                                                                                                       |           |           |   |   |
| Net revenue                                                                                                                                          | 137.4          | 136.8          | 232.2 | 237.1 |
| Operating Segments | External Customer | Gaming                                                                                                      |           |           |   |   |
| **Segment Reporting Information [Line Items]**                                                                                                       |           |           |   |   |
| Net revenue                                                                                                                                          | 245.9          | 184.3          | 495.9 | 361.6 |
| All Other                                                                                                                                            |           |           |   |   |
| **Segment Reporting Information [Line Items]**                                                                                                       |           |           |   |   |
| Net revenue                                                                                                                                          | 0.2            | 0.5            | 0.5 | 1.0 |
| All Other | External Customer                                                                                                                        |           |           |   |   |
| **Segment Reporting Information [Line Items]**                                                                                                       |           |           |   |   |
| Net revenue                                                                                                                                          | $ 0.2          | $ 0.5          | $ 0.5 | $ 1.0 |

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| - Definition
Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.
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No definition available.
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| X                                                                                                                                          |
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