Segment Information - Summary of Assets (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 2,973.5	$ 2,686.4
Operating Segments
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	1,914.0	1,870.6
Operating Segments | Live and Historical Racing
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	651.0	664.1
Operating Segments | TwinSpires
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	282.1	257.2
Operating Segments | Gaming
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	980.9	949.3
All Other
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 1,059.5	$ 815.8