Discontinued Operations - Income (Loss) From Discontinued Operations (Details) - USD ($) $ in Millions		12 Months Ended
	Jan. 09, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Transaction expense, net	$ 14.1
Gain on sale of Big Fish Games	$ 219.5
Big Fish Games | Discontinued Operations, Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net revenue		$ 13.2
Operating expenses		8.4
Selling, general and administrative expense		6.0
Research and development		0.9
Transaction expense, net		0.0
Total operating expense		15.3
Operating (loss) income		(2.1)
Gain on sale of Big Fish Games		219.5
Other expense		0.1
Total other income (loss)		219.6
Income from discontinued operations before provision for income taxes		217.5
Income tax provision		(47.3)
Income from discontinued operations, net of tax		$ 170.2
Big Fish Games | Discontinued Operations, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net revenue			$ 466.0	$ 486.2
Operating expenses			369.0	398.9
Selling, general and administrative expense			27.8	20.9
Research and development			39.6	39.0
Transaction expense, net			4.7	5.8
Total operating expense			441.1	464.6
Operating (loss) income			24.9	21.6
Gain on sale of Big Fish Games			0.0	0.0
Other expense			(1.7)	(0.9)
Total other income (loss)			(1.7)	(0.9)
Income from discontinued operations before provision for income taxes			23.2	20.7
Income tax provision			(5.1)	(9.3)
Income from discontinued operations, net of tax			$ 18.1	$ 11.4