Discontinued Operations - Income (Loss) From Discontinued Operations (Details) - Big Fish Games - Discontinued Operations, Disposed of by Sale - USD ($) $ in Millions		12 Months Ended
	Jan. 09, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net revenue		$ 0.0	$ 0.0	$ 13.2
Operating expenses		0.0	0.0	8.4
Selling, general and administrative expense		0.1	3.5	6.0
Research and development		0.0	0.0	0.9
Legal settlement	$ 14.1	124.0	0.0	0.0
Total operating expense		124.1	3.5	15.3
Operating loss		(124.1)	(3.5)	(2.1)
Gain on sale of Big Fish Games	$ 219.5	0.0	0.0	219.5
Other income		0.0	0.0	0.1
Total other income		0.0	0.0	219.6
(Loss) income from discontinued operations before provision for income taxes		(124.1)	(3.5)	217.5
Income tax benefit (provision)		28.7	1.1	(47.3)
(Loss) income from discontinued operations, net of tax		$ (95.4)	$ (2.4)	$ 170.2