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, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Net revenue	$ 278.3	$ 303.4	$ 438.5	$ 288.4	$ 272.4	$ 279.8	$ 409.2	$ 250.9	$ 1,308.6	$ 1,212.3	$ 812.2
Racing
Segment Reporting Information [Line Items]
Net revenue									251.1	248.0	261.4
Casinos
Segment Reporting Information [Line Items]
Net revenue									332.8	332.9	328.3
TwinSpires
Segment Reporting Information [Line Items]
Net revenue									220.6	200.2	191.0
Big Fish Games
Segment Reporting Information [Line Items]
Net revenue									486.2	413.7	13.9
Other Investments
Segment Reporting Information [Line Items]
Net revenue									16.9	16.6	16.5
Corporate
Segment Reporting Information [Line Items]
Net revenue									1.0	0.9	1.1
Intersegment Eliminations
Segment Reporting Information [Line Items]
Net revenue									(22.2)	(18.8)	(19.7)
Intersegment Eliminations | Racing
Segment Reporting Information [Line Items]
Net revenue									17.0	14.2	14.6
Intersegment Eliminations | TwinSpires
Segment Reporting Information [Line Items]
Net revenue									1.3	1.1	1.0
Intersegment Eliminations | Other Investments
Segment Reporting Information [Line Items]
Net revenue									3.9	3.5	4.1
Churchill Downs | Racing
Segment Reporting Information [Line Items]
Net revenue									155.2	151.1	143.2
Churchill Downs | Intersegment Eliminations | Racing
Segment Reporting Information [Line Items]
Net revenue									10.0	7.8	7.0
Arlington | Racing
Segment Reporting Information [Line Items]
Net revenue									55.3	54.4	60.3
Arlington | Intersegment Eliminations | Racing
Segment Reporting Information [Line Items]
Net revenue									5.5	5.1	5.8
Fair Grounds | Racing
Segment Reporting Information [Line Items]
Net revenue									38.0	39.8	38.6
Fair Grounds | Intersegment Eliminations | Racing
Segment Reporting Information [Line Items]
Net revenue									1.5	1.3	1.1
Calder | Racing
Segment Reporting Information [Line Items]
Net revenue									2.6	2.7	19.3
Calder | Intersegment Eliminations | Racing
Segment Reporting Information [Line Items]
Net revenue									0.0	0.0	0.7
Oxford Casino | Casinos
Segment Reporting Information [Line Items]
Net revenue									84.6	80.4	76.5
Riverwalk Casino | Casinos
Segment Reporting Information [Line Items]
Net revenue									46.1	49.8	50.1
Harlow’s Casino | Casinos
Segment Reporting Information [Line Items]
Net revenue									48.4	49.0	50.2
Calder Casinos | Casinos
Segment Reporting Information [Line Items]
Net revenue									79.1	77.4	77.0
Fair Grounds Slots | Casinos
Segment Reporting Information [Line Items]
Net revenue									36.9	39.0	40.8
VSI | Casinos
Segment Reporting Information [Line Items]
Net revenue									36.9	36.9	33.7
Saratoga | Casinos
Segment Reporting Information [Line Items]
Net revenue									0.8	0.4	0.0
Social casino | Big Fish Games
Segment Reporting Information [Line Items]
Net revenue									182.5	193.4	7.6
Casual and mid-core free-to-play | Big Fish Games
Segment Reporting Information [Line Items]
Net revenue									212.7	125.3	2.1
Premium | Big Fish Games
Segment Reporting Information [Line Items]
Net revenue									$ 91.0	$ 95.0	$ 4.2