Segment Information - Reconciliation of Comprehensive Income to Adjusted EBITDA by Segment (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Segment Reporting Information [Line Items]
Net income and comprehensive income	$ 61.0	$ 57.0	$ 359.7	$ 438.4
Depreciation and amortization	42.1	27.5	121.8	78.7
Interest expense, net	67.9	36.2	197.8	92.6
Income tax provision	20.8	16.4	130.2	173.5
EBITDA	191.8	137.1	809.5	783.2
Stock-based compensation expense	8.1	9.1	24.8	23.5
Legal reserve	0.0	0.0	0.0	3.2
Pre-opening expense	5.0	4.2	11.4	8.9
Arlington exit costs	0.1	1.4	9.4	5.7
Other expenses, net	0.7	0.0	7.6	0.0
Transaction expense, net	1.5	1.2	1.8	7.4
Asset impairments	0.0	0.0	24.5	4.9
Interest, depreciation and amortization expense related to equity investments	10.1	10.1	29.8	31.7
Changes in fair value of Rivers Des Plaines' interest rate swaps	0.0	0.0	0.0	(12.6)
Other charges and recoveries, net	0.9	0.0	0.0	1.0
Gain on sale of assets	0.0	0.0	(114.0)	(274.6)
Total adjustments to EBITDA	26.4	26.1	(4.7)	(200.3)
Adjusted EBITDA	218.2	163.2	804.8	582.9
Rivers Des Plaines
Segment Reporting Information [Line Items]
Rivers Des Plaines' legal reserves and transaction costs	0.0	0.1	0.0	0.6
Operating Segments
Segment Reporting Information [Line Items]
Adjusted EBITDA	237.1	177.2	858.9	624.9
All Other
Segment Reporting Information [Line Items]
Adjusted EBITDA	(18.9)	(14.0)	(54.1)	(42.0)
Live and Historical Racing | Operating Segments
Segment Reporting Information [Line Items]
Adjusted EBITDA	80.9	34.5	386.5	226.3
TwinSpires | Operating Segments
Segment Reporting Information [Line Items]
Adjusted EBITDA	33.9	31.1	97.2	89.1
Gaming | Operating Segments
Segment Reporting Information [Line Items]
Adjusted EBITDA	$ 122.3	$ 111.6	$ 375.2	$ 309.5