Property and Equipment (Depreciation Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Depreciation Expense	$ 15.1	$ 16.3	$ 23.2
Depreciation expense recorded in 'Cost of sales'	1.8	1.8	1.7
Loss on disposal of property and equipment	0.5	1.4	$ 0.0
Liabilities for asset retirement obligations	$ 2.8	$ 2.0