Segment Information - Reconciliation of Comprehensive Income to Adjusted EBITDA by Segment (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Net revenue	$ 515.1		$ 185.1		$ 839.4	$ 438.0
Adjusted EBITDA	233.3		30.1		343.9	85.4
Net income (loss) and comprehensive income (loss) attributable to Churchill Downs Incorporated	108.3		(118.8)		144.4	(142.2)
Net loss attributable to noncontrolling interest	0.0		0.0		0.0	0.1
Net income (loss)	108.3	$ 36.1	(118.8)	$ (23.5)	144.4	(142.3)
Loss from discontinued operations, net of tax	0.0		95.2		0.0	96.1
Income (loss) from continuing operations, net of tax	108.3		(23.6)		144.4	(46.2)
Depreciation and amortization	26.0		22.1		52.0	44.1
Interest expense	22.0		20.3		41.4	39.6
Income tax provision (benefit)	41.6		(7.9)		57.8	(19.5)
EBITDA	197.9		10.9		295.6	18.0
Stock-based compensation expense	7.1		6.1		12.6	10.4
Other charges	0.2		(0.1)		0.2	(0.1)
Pre-opening expense and other expense	1.5		1.9		2.1	3.6
Asset impairments	11.2		0.0		11.2	17.5
Transaction expense, net	0.0		0.2		0.1	0.5
Interest, depreciation and amortization expense related to equity investments	10.5		9.8		20.1	19.3
Changes in fair value of Rivers Des Plaines' interest rate swaps	(1.8)		1.3		(6.0)	16.2
Rivers Des Plaines' legal reserves and transaction costs	6.7		0.0		8.0	0.0
Total adjustments to EBITDA	35.4		19.2		48.3	67.4
Adjusted EBITDA	233.3		30.1		343.9	85.4
Operating Segments
Segment Reporting Information [Line Items]
Net revenue	515.1		185.1		839.4	438.0
Adjusted EBITDA	241.3		40.5		364.5	105.4
Adjusted EBITDA	241.3		40.5		364.5	105.4
All Other
Segment Reporting Information [Line Items]
Net revenue	17.6		3.2		27.0	13.0
Adjusted EBITDA	(8.0)		(10.4)		(20.6)	(20.0)
Adjusted EBITDA	(8.0)		(10.4)		(20.6)	(20.0)
Live and Historical Racing
Segment Reporting Information [Line Items]
Net revenue	190.5		30.3		255.2	59.4
Taxes and purses	(50.8)		(14.0)		(70.8)	(23.5)
Marketing and advertising	(4.9)		(0.3)		(7.0)	(1.5)
Salaries and benefits	(15.3)		(5.3)		(25.3)	(12.5)
Content expense	(0.8)		(0.1)		(1.4)	(0.8)
Selling, general and administrative expense	(3.1)		(1.2)		(6.1)	(2.9)
Other operating expense	(17.3)		(5.8)		(28.0)	(13.6)
Other income	0.1		0.0		0.1	0.0
Adjusted EBITDA	98.4		3.6		116.7	4.6
Asset impairments	11.2
Adjusted EBITDA	98.4		3.6		116.7	4.6
Live and Historical Racing | Operating Segments
Segment Reporting Information [Line Items]
Net revenue	175.9		23.3		239.1	51.4
Adjusted EBITDA	98.4		3.6		116.7	4.6
Adjusted EBITDA	98.4		3.6		116.7	4.6
TwinSpires
Segment Reporting Information [Line Items]
Net revenue	135.9		121.7		236.0	191.1
Taxes and purses	(8.3)		(6.7)		(14.7)	(11.0)
Marketing and advertising	(16.7)		(2.9)		(25.2)	(6.4)
Salaries and benefits	(3.2)		(3.0)		(6.3)	(6.5)
Content expense	(68.5)		(59.1)		(115.0)	(91.7)
Selling, general and administrative expense	(2.4)		(1.7)		(4.6)	(3.1)
Other operating expense	(13.7)		(9.7)		(24.6)	(17.8)
Other income	0.0		0.1		0.0	0.1
Adjusted EBITDA	23.1		38.7		45.6	54.7
Adjusted EBITDA	23.1		38.7		45.6	54.7
TwinSpires | Operating Segments
Segment Reporting Information [Line Items]
Net revenue	135.6		121.3		235.3	190.4
Adjusted EBITDA	23.1		38.7		45.6	54.7
Adjusted EBITDA	23.1		38.7		45.6	54.7
Gaming
Segment Reporting Information [Line Items]
Net revenue	186.0		37.3		340.0	184.7
Taxes and purses	(70.0)		(14.3)		(129.3)	(73.0)
Marketing and advertising	(2.5)		(0.4)		(3.9)	(5.7)
Salaries and benefits	(20.6)		(9.0)		(40.5)	(38.5)
Content expense	(1.3)		(0.4)		(2.3)	(1.4)
Selling, general and administrative expense	(5.9)		(3.9)		(11.9)	(10.6)
Other operating expense	(17.7)		(11.0)		(33.2)	(30.5)
Other income	51.8		(0.1)		83.3	21.1
Adjusted EBITDA	119.8		(1.8)		202.2	46.1
Adjusted EBITDA	119.8		(1.8)		202.2	46.1
Gaming | Operating Segments
Segment Reporting Information [Line Items]
Net revenue	186.0		37.3		338.0	183.2
Adjusted EBITDA	119.8		(1.8)		202.2	46.1
Adjusted EBITDA	$ 119.8		$ (1.8)		$ 202.2	$ 46.1