Discontinued Operations - Fair Value of Liabilities (Details) - Big Fish Games - Discontinued Operations, Held-for-sale - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Liabilities measured at fair value on a recurring basis	$ 62.6	$ 95.7
Deferred Payments
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Liabilities measured at fair value on a recurring basis	28.4	27.8
Earnout Liability
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Liabilities measured at fair value on a recurring basis	$ 34.2	$ 67.9