Discontinued Operations - Income (Loss) From Discontinued Operations (Details) - Big Fish Games - Discontinued Operations, Disposed of by Sale - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net revenue	$ 0.0	$ 13.2
Operating expenses	0.0	8.4
Selling, general and administrative expense	0.4	4.3
Research and development	0.0	0.9
Total operating expense	0.4	13.6
Operating loss	(0.4)	(0.4)
Gain on sale of Big Fish Games	0.0	219.5
Other expense	0.0	(0.1)
Total other income (expense)	0.0	219.4
(Loss) income from discontinued operations before provision for income taxes	(0.4)	219.0
Income tax benefit (provision)	0.1	(51.1)
(Loss) income from discontinued operations, net of tax	$ (0.3)	$ 167.9