Discontinued Operations (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Jan. 09, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Cash and Cash Equivalents			$ 0.3
Stock-based compensation	$ 6.1	$ 4.9
Gain (Loss) on Disposition of Business	219.5	0.0
Disposal Group, Including Discontinued Operation, Accounts, Notes and Loans Receivable, Net			34.7
Disposal Group, Including Discontinued Operation, Game Software Development, Net, Current			6.7
Disposal Group, Including Discontinued Operation, Other Assets, Current			17.0
Disposal Group, Including Discontinued Operation, Property, Plant and Equipment, Noncurrent			17.8
Disposal Group, Including Discontinued Operation, Game Software Development, Net, Noncurrent			13.8
Disposal Group, Including Discontinued Operation, Goodwill, Noncurrent			530.7
Disposal Group, Including Discontinued Operation, Intangible Assets, Noncurrent			238.4
Disposal Group, Including Discontinued Operation, Other Assets, Noncurrent			24.0
Disposal Group, Including Discontinued Operation, Accounts Payable, Current			(8.5)
Disposal Group, Including Discontinued Operation, Accrued Liabilities, Current			(22.6)
Disposal Group, Including Discontinued Operation, Deferred Revenue, Current			(44.2)
Disposal Group, Including Discontinued Operation, Deferred Tax Liabilities			(52.0)
Disposal Group, Including Discontinued Operation, Other Liabilities, Noncurrent			(4.9)
Carrying Value of Disposal Group			$ 751.2
Big Fish Games [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Stock-based compensation	3.3
Disposal Group, Including Discontinued Operation, Revenue	13.2	112.0
Disposal Group, Including Discontinued Operation, Operating Expense	8.4	87.0
Disposal Group, Including Discontinued Operation, General and Administrative Expense	4.3	5.5
Disposal Group, Including Discontinued Operations, Research And Development Expense	0.9	10.3
Disposal Group, Including Discontinued Operations, Transaction Expense	0.0	0.2
Disposal Group, Including Discontinued Operations, Total Operating Expense	13.6	103.0
Disposal Group, Including Discontinued Operation, Operating Income (Loss)	(0.4)	9.0
Disposal Group, Including Discontinued Operation, Other Expense	(0.1)	0.0
Gain (Loss) on Disposition of Business	219.5	0.0
Discontinued Operation, Income (Loss) from Discontinued Operation During Phase-out Period, before Income Tax	219.0	9.0
Discontinued Operation, Tax Effect of Income (Loss) from Discontinued Operation During Phase-out Period	(51.1)	(3.9)
Discontinued Operation, Income (Loss) from Discontinued Operation During Phase-out Period, Net of Tax	$ 167.9	$ 5.1