Quarterly Results of Operations (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended								12 Months Ended
	Aug. 31, 2018	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Net revenues		$ 280.6	$ 306.3	$ 477.4	$ 265.4	$ 219.0	$ 221.3	$ 379.4	$ 189.3	$ 1,329.7	$ 1,009.0	$ 882.6
Operating income		3.5	27.8	156.4	28.0	12.0	20.5	136.6	19.7	215.7	188.8	145.7
Income from continuing operations, net of tax		4.2	15.2	108.3	11.9	7.3	58.0	103.2	14.1	139.6	182.6	122.4
Income (loss) from discontinued operations, net of tax		$ (0.5)	$ (0.4)	$ (1.2)	$ (0.3)	$ 4.1	$ (1.7)	$ (0.1)	$ 167.9	$ (2.4)	$ 170.2	$ 18.1
Net income (loss) per common share data - basic:
Continuing operations (in dollars per share)		$ 0.11	$ 0.38	$ 2.70	$ 0.30	$ 0.18	$ 1.43	$ 2.54	$ 0.33	$ 3.49	$ 4.42	$ 2.59
Discontinued operations (in dollars per share)		(0.01)	(0.01)	(0.03)	(0.01)	0.10	(0.04)	0	3.88	(0.06)	4.12	0.38
Net income per common share - basic (in dollars per share)		0.10	0.37	2.67	0.29	0.28	1.39	2.54	4.21	3.43	8.54	2.97
Net income (loss) per common share data - diluted:
Continuing operations (in dollars per share)		0.11	0.37	2.66	0.30	0.18	1.42	2.52	0.32	3.44	4.39	2.55
Discontinued operations (in dollars per share)		(0.01)	(0.01)	(0.03)	(0.01)	0.10	(0.04)	0	3.86	(0.06)	4.09	0.37
Net income per common share - diluted (in dollars per share)		$ 0.10	$ 0.36	$ 2.63	$ 0.29	$ 0.28	$ 1.38	$ 2.52	$ 4.18	$ 3.38	$ 8.48	$ 2.92
Gain on sale of Big Fish Games									$ 219.5
Gain on Ocean Downs/Saratoga transaction	$ 54.9						$ 54.9			$ 0.0	$ 54.9	$ 0.0
Finite-Lived Intangible Assets [Line Items]
Amortization of definite-lived intangible assets										$ 15.0	$ 6.0	$ 6.8
Turfway Park
Finite-Lived Intangible Assets [Line Items]
Amortization of definite-lived intangible assets		$ 10.0