Segment Information - Total Asset Information For Segments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 1,601.0		$ 2,359.4
Capital expenditures	34.0	$ 37.5
Racing Segment [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	484.8		483.0
Capital expenditures	23.0	23.6
Casino Segment [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	678.6		679.6
Capital expenditures	3.4	8.1
TwinSpires [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	215.2		215.9
Capital expenditures	2.3	3.2
Big Fish Games [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	0.0		892.5
Capital expenditures	0.0	2.0
Other Investments Segment [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	23.0		15.2
Capital expenditures	4.6	0.4
Corporate
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	199.4		$ 73.2
Capital expenditures	$ 0.7	$ 0.2