Quarterly Results of Operations (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Net revenues	$ 219.0	$ 221.3	$ 379.4	$ 189.3	$ 178.9	$ 196.9	$ 339.3	$ 167.5	$ 1,009.0	$ 882.6	$ 822.4
Operating income	12.0	20.5	136.6	19.7	(12.8)	26.8	123.3	8.4	188.8	145.7	172.5
Income from continuing operations, net of tax	7.3	58.0	103.2	14.1	34.4	12.9	72.9	2.2	182.6	122.4	96.7
Income (loss) from discontinued operations, net of tax	$ 4.1	$ (1.7)	$ (0.1)	$ 167.9	$ 3.8	$ 3.8	$ 5.4	$ 5.1	$ 170.2	$ 18.1	$ 11.4
Net income per common share data - basic:
Continuing operations (in dollars per share)	$ 0.18	$ 1.43	$ 2.54	$ 0.33	$ 0.75	$ 0.28	$ 1.50	$ 0.04	$ 4.42	$ 2.59	$ 1.94
Discontinued operations (in dollars per share)	0.10	(0.04)	0.00	3.88	0.08	0.08	0.11	0.11	4.12	0.38	0.23
Net income per common share - basic (in dollars per share)	0.28	1.39	2.54	4.21	0.83	0.36	1.61	0.15	8.54	2.97	2.17
Net income per common share data - diluted:
Continuing operations (in dollars per share)	0.18	1.42	2.52	0.32	0.74	0.28	1.49	0.04	4.39	2.55	1.92
Discontinued operations (in dollars per share)	0.10	(0.04)	0.00	3.86	0.08	0.08	0.11	0.10	4.09	0.37	0.22
Net income per common share - diluted (in dollars per share)	$ 0.28	$ 1.38	$ 2.52	$ 4.18	$ 0.82	$ 0.36	$ 1.60	$ 0.14	$ 8.48	$ 2.92	$ 2.14
Gain on sale of Big Fish Games				$ 219.5					$ 219.5	$ 0.0	$ 0.0
Gain on Ocean Downs/Saratoga transaction		$ 54.9							54.9	0.0	0.0
Impairment of tangible and other intangible assets					$ 21.7				0.0	21.7	0.0
Loss on extinguishment of debt					20.7				0.0	20.7	0.0
Benefit from change in enacted tax rates					$ 57.7
Gain (loss) on sale of land									$ 0.0	$ 0.0	$ 23.7