Segment Information - Net Revenue From External Customers and Intercompany Revenue From Each Operating Segment (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Net revenues	$ 219.0	$ 221.3	$ 379.4	$ 189.3	$ 178.9	$ 196.9	$ 339.3	$ 167.5	$ 1,009.0	$ 882.6	$ 822.4
Racing
Segment Reporting Information [Line Items]
Net revenues									274.3	257.3	251.1
Casino
Segment Reporting Information [Line Items]
Net revenues									411.2	350.5	332.8
Online Wagering
Segment Reporting Information [Line Items]
Net revenues									290.2	255.6	221.6
Other Investments
Segment Reporting Information [Line Items]
Net revenues									33.3	19.2	16.9
Intersegment Eliminations
Segment Reporting Information [Line Items]
Net revenues									0.0	0.0	0.0
Intersegment Eliminations | Racing
Segment Reporting Information [Line Items]
Net revenues									21.1	19.3	17.0
Intersegment Eliminations | Online Wagering
Segment Reporting Information [Line Items]
Net revenues									1.3	1.1	1.3
Intersegment Eliminations | Other Investments
Segment Reporting Information [Line Items]
Net revenues									4.5	4.5	3.9
Intersegment Eliminations | Corporate
Segment Reporting Information [Line Items]
Net revenues									(26.9)	(24.9)	(22.2)
Churchill Downs | Racing
Segment Reporting Information [Line Items]
Net revenues									181.0	161.3	155.2
Churchill Downs | Intersegment Eliminations | Racing
Segment Reporting Information [Line Items]
Net revenues									12.7	11.4	10.0
Arlington | Racing
Segment Reporting Information [Line Items]
Net revenues									55.0	57.2	55.3
Arlington | Intersegment Eliminations | Racing
Segment Reporting Information [Line Items]
Net revenues									6.7	6.3	5.5
Fair Grounds | Racing
Segment Reporting Information [Line Items]
Net revenues									35.8	36.3	38.0
Fair Grounds | Intersegment Eliminations | Racing
Segment Reporting Information [Line Items]
Net revenues									1.6	1.6	1.5
Calder Racing | Racing
Segment Reporting Information [Line Items]
Net revenues									2.5	2.5	2.6
Calder Racing | Intersegment Eliminations | Racing
Segment Reporting Information [Line Items]
Net revenues									0.1	0.0	0.0
Oxford | Casino
Segment Reporting Information [Line Items]
Net revenues									102.0	90.8	84.6
Calder | Casino
Segment Reporting Information [Line Items]
Net revenues									96.1	85.4	79.1
Fair Grounds Slots and VSI | Casino
Segment Reporting Information [Line Items]
Net revenues									81.9	74.8	73.8
Riverwalk | Casino
Segment Reporting Information [Line Items]
Net revenues									54.5	48.2	46.1
Harlow’s | Casino
Segment Reporting Information [Line Items]
Net revenues									50.2	50.0	48.4
Ocean Downs | Casino
Segment Reporting Information [Line Items]
Net revenues									25.9	0.0	0.0
Saratoga | Casino
Segment Reporting Information [Line Items]
Net revenues									$ 0.6	$ 1.3	$ 0.8