Discontinued Operations - Change in Fair Value of Liabilities (Details) - Big Fish Games - Discontinued Operations, Held-for-sale $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance as of December 31, 2016	$ 95.7
Payments	(34.2)
Change in fair value	1.1
Balance as of December 31, 2017	62.6
Deferred Payments
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance as of December 31, 2016	27.8
Payments	0.0
Change in fair value	0.6
Balance as of December 31, 2017	28.4
Earnout Liability
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance as of December 31, 2016	67.9
Payments	(34.2)
Change in fair value	0.5
Balance as of December 31, 2017	$ 34.2