Pension and Other Post-Retirement Plans - Net Periodic Benefit Cost (Details) (Defined benefit pension plans, USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined benefit pension plans
Components of net periodic pension benefit cost:
Service cost	$ 2.2	$ 2.5	$ 2.1
Interest cost	4.9	4.7	4.7
Expected return on plan assets	(6.6)	(5.5)	(5.2)
Amortization of actuarial gains/losses	0.6	1.0	0.8
Curtailments	0.1	0.1	0
Amortization of unrecognized prior service cost	(0.2)	(0.3)	(0.2)
Net periodic cost	$ 1.0	$ 2.5	$ 2.2