Segment Information - Reconciliation of Comprehensive Income to Adjusted EBITDA (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
	Aug. 31, 2018	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Comprehensive (loss) income attributable to Churchill Downs Incorporated										$ (81.9)	$ 137.5	$ 353.2
Foreign currency translation, net of tax										0.0	0.0	(0.6)
Change in pension benefits, net of tax										0.0	0.0	0.2
Net (loss) income attributable to Churchill Downs Incorporated										(81.9)	137.5	352.8
Net loss attributable to noncontrolling interest										0.2	0.3	0.0
Net (loss) income before noncontrolling interest										(82.1)	137.2	352.8
Loss (income) from discontinued operations, net of tax		$ (0.7)	$ 0.0	$ 95.2	$ 0.9	$ 0.5	$ 0.4	$ 1.2	$ 0.3	95.4	2.4	(170.2)
(Loss) income from continuing operations, net of tax		$ 16.4	$ 43.1	$ (23.6)	$ (22.6)	$ 4.2	$ 15.2	$ 108.3	$ 11.9	13.3	139.6	182.6
Depreciation and amortization										92.9	96.4	63.6
Income tax (benefit) provision										(5.3)	56.8	51.3
EBITDA										180.9	363.7	337.6
Stock-based compensation expense										23.7	23.8	21.1
Legal reserves										0.0	3.6	0.0
Changes in fair value of Midwest Gaming's interest rate swaps										12.9	12.4	0.0
Midwest Gaming's recapitalization and transactions costs										0.0	4.7	0.0
Gain on Ocean Downs/Saratoga transaction	$ (54.9)									0.0	0.0	(54.9)
Impairment of tangible and other intangible assets										17.5	0.0	0.0
Total adjustments to EBITDA										105.6	87.7	(8.8)
Adjusted EBITDA										286.5	451.4	328.8
Operating Segments
Segment Reporting Information [Line Items]
Adjusted EBITDA										324.3	484.9	355.4
All Other
Segment Reporting Information [Line Items]
Adjusted EBITDA										(37.8)	(33.5)	(26.6)
Churchill Downs | Operating Segments
Segment Reporting Information [Line Items]
Adjusted EBITDA										38.3	137.7	102.4
Online Wagering | Operating Segments
Segment Reporting Information [Line Items]
Adjusted EBITDA										109.3	66.3	79.0
Gaming | Operating Segments
Segment Reporting Information [Line Items]
Adjusted EBITDA										176.7	280.9	174.0
Continuing Operations
Segment Reporting Information [Line Items]
Depreciation and amortization										92.9	96.4	63.6
Interest expense										80.0	70.9	40.1
Income tax (benefit) provision										(5.3)	56.8	51.3
Stock-based compensation expense										23.7	23.8	17.7
Other, net										0.8	0.4	(0.6)
Pre-opening expense										11.2	5.1	4.8
Interest, depreciation and amortization expense related to equity investments										38.5	32.6	13.9
Other charges and recoveries, net										0.0	(0.2)	0.0
Gain on Ocean Downs/Saratoga transaction										0.0	0.0	(54.9)
Transaction expense, net										1.0	5.3	10.3
Impairment of tangible and other intangible assets										$ 17.5	$ 0.0	$ 0.0