Condensed Consolidated Statements Of Comprehensive Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Net revenue:
Racing	$ 38.8	$ 38.5	$ 228.0	$ 220.8
Casinos	87.5	83.0	263.3	253.9
TwinSpires	65.9	55.1	198.4	173.1
Big Fish Games	117.9	122.3	342.5	369.6
Other Investments	4.7	4.5	14.0	12.9
Total net revenue	314.8	303.4	1,046.2	1,030.3
Operating expense:
Racing	40.8	41.5	153.7	149.4
Casinos	60.7	61.4	185.5	182.8
TwinSpires	42.8	36.8	130.6	112.8
Big Fish Games	95.2	94.5	271.5	309.5
Other Investments	4.3	3.9	13.1	11.9
Corporate	0.6	0.5	1.8	1.5
Selling, general and administrative expense	26.8	27.6	77.6	75.3
Research and development	9.7	8.8	29.9	29.3
Calder exit costs	0.2	0.5	0.8	2.4
Acquisition expense, net	0.7	1.1	1.7	4.9
Total operating expense	281.8	276.6	866.2	879.8
Operating income	33.0	26.8	180.0	150.5
Other income (expense):
Interest expense	(12.6)	(11.1)	(36.0)	(32.8)
Equity in income of unconsolidated investments	8.9	4.9	22.7	13.5
Miscellaneous, net	(1.0)	(0.2)	(0.8)	(0.3)
Total other income (expense)	(4.7)	(6.4)	(14.1)	(19.6)
Income (loss) from operations before provision for income taxes	28.3	20.4	165.9	130.9
Income tax provision	(11.6)	(11.7)	(63.6)	(49.6)
Net income	$ 16.7	$ 8.7	$ 102.3	$ 81.3
Earnings Per Share, Basic [Abstract]
Basic	$ 1.09	$ 0.52	$ 6.43	$ 4.85
Earnings Per Share, Diluted [Abstract]
Diluted	$ 1.08	$ 0.52	$ 6.32	$ 4.79
Weighted average shares outstanding:
Basic-weighted average shares	15.3	16.4	15.9	16.5
Diluted (in shares)	15.5	16.9	16.2	17.0
Other comprehensive loss:
Foreign currency translation, net of tax	$ 0.5	$ 0.0	$ 0.1	$ 0.2
Change in pension benefits, net of tax	0.1	0.0	0.1	0.0
Other comprehensive gain	0.6	0.0	0.2	0.2
Comprehensive income	$ 17.3	$ 8.7	$ 102.5	$ 81.5