Discontinued Operations (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 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	$ 6.4	$ 4.4	$ 12.6	$ 11.7
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			3.4
Disposal Group, Including Discontinued Operation, Revenue	0.0	112.5	13.2	224.5
Disposal Group, Including Discontinued Operation, Operating Expense	0.0	89.2	8.4	176.2
Disposal Group, Including Discontinued Operation, General and Administrative Expense	0.6	6.7	4.9	12.2
Disposal Group, Including Discontinued Operations, Research And Development Expense	0.0	9.9	0.9	20.2
Disposal Group, Including Discontinued Operations, Transaction Expense	0.0	0.2	0.0	0.4
Disposal Group, Including Discontinued Operations, Total Operating Expense	0.6	106.0	14.2	209.0
Disposal Group, Including Discontinued Operation, Operating Income (Loss)	(0.6)	6.5	(1.0)	15.5
Disposal Group, Including Discontinued Operation, Other Expense	0.0	(0.4)	(0.1)	(0.4)
Disposal Group, Including Discontinued Operation, Other Income	0.0	(0.4)	219.4	(0.4)
Gain (Loss) on Disposition of Business	0.0	0.0	219.5	0.0
Discontinued Operation, Income (Loss) from Discontinued Operation During Phase-out Period, before Income Tax	(0.6)	6.1	218.4	15.1
Discontinued Operation, Tax Effect of Income (Loss) from Discontinued Operation During Phase-out Period	0.5	(0.5)	(50.6)	(4.4)
Discontinued Operation, Income (Loss) from Discontinued Operation During Phase-out Period, Net of Tax	$ (0.1)	$ 5.6	$ 167.8	$ 10.7