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, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Net revenues	$ 178.9	$ 196.9	$ 339.3	$ 167.5	$ 161.8	$ 181.0	$ 313.3	$ 166.3	$ 882.6	$ 822.4	$ 798.6
Racing
Segment Reporting Information [Line Items]
Net revenues									257.3	251.1	248.0
Casino
Segment Reporting Information [Line Items]
Net revenues									350.5	332.8	332.9
TwinSpires
Segment Reporting Information [Line Items]
Net revenues									255.6	221.6	201.1
Other Investments
Segment Reporting Information [Line Items]
Net revenues									19.2	16.9	16.6
Corporate
Segment Reporting Information [Line Items]
Net revenues									0.0	0.0	0.0
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									19.3	17.0	14.2
Intersegment Eliminations | TwinSpires
Segment Reporting Information [Line Items]
Net revenues									1.1	1.3	1.1
Intersegment Eliminations | Other Investments
Segment Reporting Information [Line Items]
Net revenues									4.5	3.9	3.5
Intersegment Eliminations | Corporate
Segment Reporting Information [Line Items]
Net revenues									(24.9)	(22.2)	(18.8)
Churchill Downs | Racing
Segment Reporting Information [Line Items]
Net revenues									161.3	155.2	151.1
Churchill Downs | Intersegment Eliminations | Racing
Segment Reporting Information [Line Items]
Net revenues									11.4	10.0	7.8
Arlington | Racing
Segment Reporting Information [Line Items]
Net revenues									57.2	55.3	54.4
Arlington | Intersegment Eliminations | Racing
Segment Reporting Information [Line Items]
Net revenues									6.3	5.5	5.1
Fair Grounds | Racing
Segment Reporting Information [Line Items]
Net revenues									36.3	38.0	39.8
Fair Grounds | Intersegment Eliminations | Racing
Segment Reporting Information [Line Items]
Net revenues									1.6	1.5	1.3
Calder | Racing
Segment Reporting Information [Line Items]
Net revenues									2.5	2.6	2.7
Calder | Intersegment Eliminations | Racing
Segment Reporting Information [Line Items]
Net revenues									0.0	0.0	0.0
Oxford Casino | Casino
Segment Reporting Information [Line Items]
Net revenues									90.8	84.6	80.4
Riverwalk Casino | Casino
Segment Reporting Information [Line Items]
Net revenues									48.2	46.1	49.8
Harlow’s Casino | Casino
Segment Reporting Information [Line Items]
Net revenues									50.0	48.4	49.0
Calder Casinos | Casino
Segment Reporting Information [Line Items]
Net revenues									85.4	79.1	77.4
Fair Grounds Slots | Casino
Segment Reporting Information [Line Items]
Net revenues									36.5	36.9	39.0
VSI | Casino
Segment Reporting Information [Line Items]
Net revenues									38.3	36.9	36.9
Saratoga | Casino
Segment Reporting Information [Line Items]
Net revenues									$ 1.3	$ 0.8	$ 0.4