Condensed Consolidated Statements Of Comprehensive Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Net revenue:
Racing	$ 165.3	$ 156.1	$ 189.2	$ 182.3
Casinos	88.3	84.4	175.8	170.9
TwinSpires	80.5	68.4	132.5	118.0
Big Fish Games	112.6	125.2	224.6	247.3
Other Investments	5.2	4.4	9.3	8.4
Total net revenue	451.9	438.5	731.4	726.9
Operating expense:
Racing	76.5	72.3	112.9	107.9
Casinos	62.1	60.4	124.8	121.4
TwinSpires	51.4	41.4	87.8	76.0
Big Fish Games	89.4	105.6	176.3	215.0
Other Investments	4.9	4.1	8.8	8.0
Corporate	0.5	0.4	1.2	1.0
Selling, general and administrative expense	26.7	24.6	50.8	47.7
Research and development	9.9	9.7	20.2	20.5
Calder exit costs	0.2	1.5	0.6	1.9
Acquisition expenses, net	0.8	1.1	1.0	3.8
Total operating expense	322.4	321.1	584.4	603.2
Operating income	129.5	117.4	147.0	123.7
Other income (expense):
Interest expense	(11.6)	(11.1)	(23.4)	(21.7)
Equity in income of unconsolidated investments	7.7	4.8	13.8	8.6
Miscellaneous, net	0.2	0.4	0.2	(0.1)
Total other expense	(3.7)	(5.9)	(9.4)	(13.2)
Income (loss) from operations before provision for income taxes	125.8	111.5	137.6	110.5
Income tax provision	(47.5)	(41.7)	(52.0)	(37.9)
Net income	$ 78.3	$ 69.8	$ 85.6	$ 72.6
Earnings Per Share, Basic [Abstract]
Basic	$ 4.86	$ 4.16	$ 5.27	$ 4.32
Earnings Per Share, Diluted [Abstract]
Diluted	$ 4.81	$ 4.11	$ 5.18	$ 4.27
Weighted average shares outstanding:
Basic	16.1	16.5	16.2	16.5
Diluted (in shares)	16.3	17.0	16.5	17.0
Other comprehensive loss:
Foreign currency translation, net of tax	$ (0.3)	$ 0.2	$ (0.4)	$ 0.2
Other comprehensive (loss) gain	(0.3)	0.2	(0.4)	0.2
Comprehensive income	$ 78.0	$ 70.0	$ 85.2	$ 72.8