Condensed Consolidated Statements Of Comprehensive Earnings - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Net revenue:
Racing	$ 38.5	$ 38.8	$ 220.8	$ 218.0
Casinos	83.0	82.7	253.9	252.5
TwinSpires	54.7	50.4	172.3	156.5
Big Fish Games	122.3	103.6	369.6	300.0
Other Investments	4.5	4.0	12.9	12.1
Corporate	0.4	0.3	0.8	0.8
Total net revenue	303.4	279.8	1,030.3	939.9
Operating expense:
Racing	41.5	41.0	149.4	152.3
Casinos	61.4	60.8	182.8	182.9
TwinSpires	36.8	33.9	112.8	104.6
Big Fish Games	94.5	80.0	309.5	245.6
Other Investments	3.9	4.1	11.9	11.8
Corporate	0.5	0.5	1.5	2.3
Selling, general and administrative expense	27.6	24.7	75.3	68.3
Research and development	8.8	9.9	29.3	30.0
Calder exit costs	0.5	12.7	2.4	13.5
Acquisition-related charges	1.1	2.8	4.9	17.4
Total operating expense	276.6	270.4	879.8	828.7
Operating income	26.8	9.4	150.5	111.2
Other income (expense):
Interest income	0.0	0.0	0.0	0.2
Interest expense	(11.1)	(6.7)	(32.8)	(21.3)
Equity in income of unconsolidated investments	4.9	2.3	13.5	8.2
Miscellaneous, net	(0.2)	(0.1)	(0.3)	5.5
Total other income (expense)	(6.4)	(4.5)	(19.6)	(7.4)
Income before income tax provision	20.4	4.9	130.9	103.8
Income tax provision	(11.7)	(0.7)	(49.6)	(46.1)
Net income	$ 8.7	$ 4.2	$ 81.3	$ 57.7
Earnings Per Share, Basic [Abstract]
Basic	$ 0.52	$ 0.24	$ 4.85	$ 3.28
Earnings Per Share, Diluted [Abstract]
Diluted	$ 0.52	$ 0.24	$ 4.79	$ 3.26
Weighted average shares outstanding:
Basic	16.4	17.3	16.5	17.3
Diluted (in shares)	16.9	17.8	17.0	17.7
Other comprehensive income (loss):
Foreign currency translation, net of tax	$ 0.0	$ 0.0	$ 0.2	$ (0.4)
Other comprehensive income (loss)	0.0	0.0	0.2	(0.4)
Comprehensive income	$ 8.7	$ 4.2	$ 81.5	$ 57.3