Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Net deferred tax liability	$ 3.1	$ 3.1
Income tax receivable	1.3	9.1
Net operating loss carryforwards	805.4
Foreign tax credit carryforwards, subject to expriration	0.9
Capital loss carryforward, expiring in 2021	13.8
Valuation allowance	305.1	461.7
Deferred income tax benefit	13.3		$ 11.7
Unrecognized tax benefits that would impact effective tax rate	10.8	10.9
Unrecognized Tax Benefits, Interest on Income Taxes Expense	0.8	0.6
Interest accrual reversal	0.7	1.5
Interest accrued net reduction	0.1	0.9
Total amount of interest accrued for uncertain tax positions	2.3	$ 2.2
Amount by which unrecognized tax benefits may decrease over the next 12 months	$ 0.6