Segment Information - Net Revenue From External Customers and Intercompany Revenue From Each Operating Segment (Details) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019 USD ($) segment	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) segment	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Segment Reporting [Abstract]
Number of reportable segments | segment	3								3
Segment Reporting Information [Line Items]
Net revenues	$ 280.6	$ 306.3	$ 477.4	$ 265.4	$ 219.0	$ 221.3	$ 379.4	$ 189.3	$ 1,329.7	$ 1,009.0	$ 882.6
Intercompany net revenues									0.0	0.0	0.0
Other revenue									33.4	26.1	21.5
External Customer
Segment Reporting Information [Line Items]
Net revenues									1,329.7	1,009.0	882.6
External Customer | Pari-mutuel, live and simulcast racing
Segment Reporting Information [Line Items]
Net revenues									407.9	403.5	363.5
External Customer | Historical racing
Segment Reporting Information [Line Items]
Net revenues									81.6	13.8	0.0
External Customer | Racing event-related services
Segment Reporting Information [Line Items]
Net revenues									128.4	124.9	111.1
External Customer | Gaming
Segment Reporting Information [Line Items]
Net revenues									585.8	365.9	315.6
External Customer | Other
Segment Reporting Information [Line Items]
Net revenues									126.0	100.9	92.4
Churchill Downs
Segment Reporting Information [Line Items]
Net revenues									289.4	208.5	172.7
Online Wagering
Segment Reporting Information [Line Items]
Net revenues									291.6	291.5	256.7
Gaming
Segment Reporting Information [Line Items]
Net revenues									694.8	451.2	390.9
Operating Segments
Segment Reporting Information [Line Items]
Net revenues									1,329.7	1,009.0	882.6
Operating Segments | Total Segments | External Customer
Segment Reporting Information [Line Items]
Net revenues									1,257.1	935.5	806.2
Operating Segments | Total Segments | External Customer | Pari-mutuel, live and simulcast racing
Segment Reporting Information [Line Items]
Net revenues									366.8	360.4	318.7
Operating Segments | Total Segments | External Customer | Historical racing
Segment Reporting Information [Line Items]
Net revenues									81.6	13.8	0.0
Operating Segments | Total Segments | External Customer | Racing event-related services
Segment Reporting Information [Line Items]
Net revenues									122.8	119.1	104.7
Operating Segments | Total Segments | External Customer | Gaming
Segment Reporting Information [Line Items]
Net revenues									585.8	365.9	315.6
Operating Segments | Total Segments | External Customer | Other
Segment Reporting Information [Line Items]
Net revenues									100.1	76.3	67.2
Operating Segments | Churchill Downs
Segment Reporting Information [Line Items]
Net revenues									274.2	195.8	161.3
Intercompany net revenues									15.2	12.7	11.4
Operating Segments | Churchill Downs | External Customer
Segment Reporting Information [Line Items]
Net revenues									274.2	195.8	161.3
Operating Segments | Churchill Downs | External Customer | Pari-mutuel, live and simulcast racing
Segment Reporting Information [Line Items]
Net revenues									59.0	54.9	52.0
Operating Segments | Churchill Downs | External Customer | Historical racing
Segment Reporting Information [Line Items]
Net revenues									81.6	13.8	0.0
Operating Segments | Churchill Downs | External Customer | Racing event-related services
Segment Reporting Information [Line Items]
Net revenues									118.7	115.2	100.5
Operating Segments | Churchill Downs | External Customer | Gaming
Segment Reporting Information [Line Items]
Net revenues									0.0	0.0	0.0
Operating Segments | Churchill Downs | External Customer | Other
Segment Reporting Information [Line Items]
Net revenues									14.9	11.9	8.8
Operating Segments | Churchill Downs | Churchill Downs Racetrack
Segment Reporting Information [Line Items]
Net revenues									187.6	181.0	161.3
Operating Segments | Churchill Downs | Derby City Gaming
Segment Reporting Information [Line Items]
Net revenues									86.6	14.8	0.0
Operating Segments | Online Wagering
Segment Reporting Information [Line Items]
Net revenues									290.5	290.2	255.6
Intercompany net revenues									1.1	1.3	1.1
Operating Segments | Online Wagering | External Customer
Segment Reporting Information [Line Items]
Net revenues									290.5	290.2	255.6
Operating Segments | Online Wagering | External Customer | Pari-mutuel, live and simulcast racing
Segment Reporting Information [Line Items]
Net revenues									277.1	278.4	239.6
Operating Segments | Online Wagering | External Customer | Historical racing
Segment Reporting Information [Line Items]
Net revenues									0.0	0.0	0.0
Operating Segments | Online Wagering | External Customer | Racing event-related services
Segment Reporting Information [Line Items]
Net revenues									0.0	0.0	0.0
Operating Segments | Online Wagering | External Customer | Gaming
Segment Reporting Information [Line Items]
Net revenues									0.6	0.0	0.0
Operating Segments | Online Wagering | External Customer | Other
Segment Reporting Information [Line Items]
Net revenues									12.8	11.8	16.0
Operating Segments | Online Wagering | TwinSpires
Segment Reporting Information [Line Items]
Net revenues									289.9	290.2	255.6
Operating Segments | Online Wagering | Online Sports Betting and iGaming
Segment Reporting Information [Line Items]
Net revenues									0.6	0.0	0.0
Operating Segments | Gaming
Segment Reporting Information [Line Items]
Net revenues									692.4	449.5	389.3
Intercompany net revenues									2.4	1.7	1.6
Operating Segments | Gaming | External Customer
Segment Reporting Information [Line Items]
Net revenues									692.4	449.5	389.3
Operating Segments | Gaming | External Customer | Pari-mutuel, live and simulcast racing
Segment Reporting Information [Line Items]
Net revenues									30.7	27.1	27.1
Operating Segments | Gaming | External Customer | Historical racing
Segment Reporting Information [Line Items]
Net revenues									0.0	0.0	0.0
Operating Segments | Gaming | External Customer | Racing event-related services
Segment Reporting Information [Line Items]
Net revenues									4.1	3.9	4.2
Operating Segments | Gaming | External Customer | Gaming
Segment Reporting Information [Line Items]
Net revenues									585.2	365.9	315.6
Operating Segments | Gaming | External Customer | Other
Segment Reporting Information [Line Items]
Net revenues									72.4	52.6	42.4
Operating Segments | Gaming | Oxford Casino
Segment Reporting Information [Line Items]
Net revenues									101.7	102.0	90.8
Operating Segments | Gaming | Riverwalk Casino
Segment Reporting Information [Line Items]
Net revenues									58.9	54.5	48.2
Operating Segments | Gaming | Harlow’s Casino
Segment Reporting Information [Line Items]
Net revenues									55.3	50.2	50.0
Operating Segments | Gaming | Calder
Segment Reporting Information [Line Items]
Net revenues									99.8	98.6	87.9
Intercompany net revenues									0.1	0.1	0.0
Operating Segments | Gaming | Fair Grounds and VSI
Segment Reporting Information [Line Items]
Net revenues									123.0	117.7	111.1
Intercompany net revenues									1.8	1.6	1.6
Operating Segments | Gaming | Saratoga
Segment Reporting Information [Line Items]
Net revenues									0.0	0.6	1.3
Operating Segments | Gaming | Lady Luck Nemacolin
Segment Reporting Information [Line Items]
Net revenues									29.3	0.0	0.0
Operating Segments | Gaming | Presque Isle
Segment Reporting Information [Line Items]
Net revenues									138.5	0.0	0.0
Intercompany net revenues									0.5	0.0	0.0
Operating Segments | Gaming | Ocean Downs
Segment Reporting Information [Line Items]
Net revenues									85.9	25.9	0.0
All Other | All Other
Segment Reporting Information [Line Items]
Net revenues									72.6	73.5	76.4
Intercompany net revenues									11.6	11.2	10.8
All Other | All Other | External Customer
Segment Reporting Information [Line Items]
Net revenues									72.6	73.5	76.4
All Other | All Other | External Customer | Pari-mutuel, live and simulcast racing
Segment Reporting Information [Line Items]
Net revenues									41.1	43.1	44.8
All Other | All Other | External Customer | Historical racing
Segment Reporting Information [Line Items]
Net revenues									0.0	0.0	0.0
All Other | All Other | External Customer | Racing event-related services
Segment Reporting Information [Line Items]
Net revenues									5.6	5.8	6.4
All Other | All Other | External Customer | Gaming
Segment Reporting Information [Line Items]
Net revenues									0.0	0.0	0.0
All Other | All Other | External Customer | Other
Segment Reporting Information [Line Items]
Net revenues									25.9	24.6	25.2
Intersegment Eliminations
Segment Reporting Information [Line Items]
Intercompany net revenues									$ (30.3)	$ (26.9)	$ (24.9)