Employee Benefit Plans - Amounts Recognized in Consolidated Balance Sheets and Accumulated Other Comprehensive Loss (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Amounts recognized on the consolidated balance sheets [Abstract]
Non-current liabilities	$ (54.8)	$ (37.3)
Amounts recognized in accumulated other comprehensive loss [Abstract]
Total	(44.4)	(30.1)	(47.2)
Pension Benefits
Amounts recognized on the consolidated balance sheets [Abstract]
Non-current assets	0	3.3
Current liabilities	0	0
Non-current liabilities	(43.6)	(25.3)
Total	(43.6)	(22.0)
Amounts recognized in accumulated other comprehensive loss [Abstract]
Net loss (net of taxes)	47.3	33.2
Unrecognized prior service credit (net of taxes)	(3.4)	(3.9)
Total	43.9	29.3
Other Post-retirement Benefits
Amounts recognized on the consolidated balance sheets [Abstract]
Non-current assets	0	0
Current liabilities	(0.8)	(0.9)
Non-current liabilities	(11.2)	(12.0)
Total	(12.0)	(12.9)
Amounts recognized in accumulated other comprehensive loss [Abstract]
Net loss (net of taxes)	0.5	1.1
Unrecognized prior service credit (net of taxes)	0	0
Total	$ 0.5	$ 1.1