Pension and Post-retirement and Other Benefit Plans - Pension and Other Postretirement Benefit Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pensions
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1.7	$ 1.4	$ 1.5
Interest cost	10.7	11.4	13.7
Expected return on plan assets	(17.1)	(18.0)	(19.1)
Settlement charge	0.0	0.1	0.3
Amortization of prior service credit	0.0	0.0	0.0
Amortization of net actuarial loss	4.3	4.1	4.5
Total (income) costs	(0.4)	(1.0)	0.9
Other post-retirement benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.0	0.0	0.0
Interest cost	0.1	0.1	0.2
Amortization of prior service credit	0.0	0.0	(2.5)
Amortization of net actuarial loss	0.0	0.0	0.0
Total (income) costs	$ 0.1	$ 0.1	$ (2.3)