Income Taxes - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Taxes [Line Items]
Change in tax rate income tax expense (benefit)	$ 56.9
Transition tax for accumulated foreign earnings, income tax expense (benefit)	0.8
Non-deductible officer's compensation provisional income tax expense	4.7
Tax depreciation provisional income tax benefit	19.7
Transition tax for accumulated foreign earnings provisional income tax expense	0.9
Change in tax rate provisional tax expense (benefit)	56.9
Unrecognized tax benefits	2.9	$ 2.3	$ 1.8	$ 1.5
Unrecognized tax benefits that would impact effective tax rate	2.8
Anticipated decrease in unrecognized tax positions	0.2
Federal | Youbet.com
Income Taxes [Line Items]
Operating loss carryforwards	9.6
State
Income Taxes [Line Items]
Operating loss carryforwards	2.1
Operating loss carryforwards, valuation allowance	0.2
State | Youbet.com
Income Taxes [Line Items]
Operating loss carryforwards	$ 0.5