Segment Information - Schedule of Net Revenue from External Customers (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Net revenue from external customers	$ 265.4	$ 189.3
Churchill Downs
Segment Reporting Information [Line Items]
Net revenue from external customers	21.4	2.3
Online Wagering
Segment Reporting Information [Line Items]
Net revenue from external customers	63.4	63.6
Gaming
Segment Reporting Information [Line Items]
Net revenue from external customers	170.1	112.5
Operating Segments
Segment Reporting Information [Line Items]
Net revenue from external customers	265.4	189.3
Operating Segments | Churchill Downs
Segment Reporting Information [Line Items]
Net revenue from external customers	21.0	2.0
Operating Segments | Online Wagering
Segment Reporting Information [Line Items]
Net revenue from external customers	63.1	63.2
Operating Segments | Gaming
Segment Reporting Information [Line Items]
Net revenue from external customers	168.8	111.5
Segment Reconciling Items | All Other
Segment Reporting Information [Line Items]
Net revenue from external customers	12.5	12.6
Gaming
Segment Reporting Information [Line Items]
Net revenue from external customers	168.8	111.5
Other
Segment Reporting Information [Line Items]
Net revenue from external customers	12.5	12.6
External Customer
Segment Reporting Information [Line Items]
Net revenue from external customers	265.4	189.3
External Customer | Operating Segments | Churchill Downs
Segment Reporting Information [Line Items]
Net revenue from external customers	21.0	2.0
External Customer | Operating Segments | Online Wagering
Segment Reporting Information [Line Items]
Net revenue from external customers	63.1	63.2
External Customer | Operating Segments | Gaming
Segment Reporting Information [Line Items]
Net revenue from external customers	168.8	111.5
External Customer | Operating Segments | Total Segments
Segment Reporting Information [Line Items]
Net revenue from external customers	252.9	176.7
External Customer | Segment Reconciling Items | All Other
Segment Reporting Information [Line Items]
Net revenue from external customers	12.5	12.6
External Customer | Pari-mutuel, live and simulcast racing
Segment Reporting Information [Line Items]
Net revenue from external customers	81.6	80.8
External Customer | Pari-mutuel, live and simulcast racing | Operating Segments | Churchill Downs
Segment Reporting Information [Line Items]
Net revenue from external customers	1.4	1.3
External Customer | Pari-mutuel, live and simulcast racing | Operating Segments | Online Wagering
Segment Reporting Information [Line Items]
Net revenue from external customers	60.5	61.0
External Customer | Pari-mutuel, live and simulcast racing | Operating Segments | Gaming
Segment Reporting Information [Line Items]
Net revenue from external customers	12.2	10.6
External Customer | Pari-mutuel, live and simulcast racing | Operating Segments | Total Segments
Segment Reporting Information [Line Items]
Net revenue from external customers	74.1	72.9
External Customer | Pari-mutuel, live and simulcast racing | Segment Reconciling Items | All Other
Segment Reporting Information [Line Items]
Net revenue from external customers	7.5	7.9
External Customer | Pari-mutuel, historical racing
Segment Reporting Information [Line Items]
Net revenue from external customers	17.7	0.0
External Customer | Pari-mutuel, historical racing | Operating Segments | Churchill Downs
Segment Reporting Information [Line Items]
Net revenue from external customers	17.7	0.0
External Customer | Pari-mutuel, historical racing | Operating Segments | Online Wagering
Segment Reporting Information [Line Items]
Net revenue from external customers	0.0	0.0
External Customer | Pari-mutuel, historical racing | Operating Segments | Gaming
Segment Reporting Information [Line Items]
Net revenue from external customers	0.0	0.0
External Customer | Pari-mutuel, historical racing | Operating Segments | Total Segments
Segment Reporting Information [Line Items]
Net revenue from external customers	17.7	0.0
External Customer | Pari-mutuel, historical racing | Segment Reconciling Items | All Other
Segment Reporting Information [Line Items]
Net revenue from external customers	0.0	0.0
External Customer | Racing event-related services
Segment Reporting Information [Line Items]
Net revenue from external customers	1.5	1.4
External Customer | Racing event-related services | Operating Segments | Churchill Downs
Segment Reporting Information [Line Items]
Net revenue from external customers	0.0	0.0
External Customer | Racing event-related services | Operating Segments | Online Wagering
Segment Reporting Information [Line Items]
Net revenue from external customers	0.0	0.0
External Customer | Racing event-related services | Operating Segments | Gaming
Segment Reporting Information [Line Items]
Net revenue from external customers	1.5	1.4
External Customer | Racing event-related services | Operating Segments | Total Segments
Segment Reporting Information [Line Items]
Net revenue from external customers	1.5	1.4
External Customer | Racing event-related services | Segment Reconciling Items | All Other
Segment Reporting Information [Line Items]
Net revenue from external customers	0.0	0.0
External Customer | Gaming
Segment Reporting Information [Line Items]
Net revenue from external customers	146.7	93.9
External Customer | Gaming | Operating Segments | Churchill Downs
Segment Reporting Information [Line Items]
Net revenue from external customers	0.0	0.0
External Customer | Gaming | Operating Segments | Online Wagering
Segment Reporting Information [Line Items]
Net revenue from external customers	0.1	0.0
External Customer | Gaming | Operating Segments | Gaming
Segment Reporting Information [Line Items]
Net revenue from external customers	146.6	93.9
External Customer | Gaming | Operating Segments | Total Segments
Segment Reporting Information [Line Items]
Net revenue from external customers	146.7	93.9
External Customer | Gaming | Segment Reconciling Items | All Other
Segment Reporting Information [Line Items]
Net revenue from external customers	0.0	0.0
External Customer | Other
Segment Reporting Information [Line Items]
Net revenue from external customers	17.9	13.2
External Customer | Other | Operating Segments | Churchill Downs
Segment Reporting Information [Line Items]
Net revenue from external customers	1.9	0.7
External Customer | Other | Operating Segments | Online Wagering
Segment Reporting Information [Line Items]
Net revenue from external customers	2.5	2.2
External Customer | Other | Operating Segments | Gaming
Segment Reporting Information [Line Items]
Net revenue from external customers	8.5	5.6
External Customer | Other | Operating Segments | Total Segments
Segment Reporting Information [Line Items]
Net revenue from external customers	12.9	8.5
External Customer | Other | Segment Reconciling Items | All Other
Segment Reporting Information [Line Items]
Net revenue from external customers	$ 5.0	$ 4.7