Pension and Postretirement Benefits (Components of net periodic benefit) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Pension Benefits
Components of net periodic benefit cost
Service costs	$ 1.1	$ 1.1
Interest costs	0.3	0.5
Expected return on plan assets	(3.1)	(2.9)
Recognized net actuarial loss	0.2	0.5
Net periodic benefit (income) expense	(1.5)	(0.8)
Postretirement Benefits
Components of net periodic benefit cost
Service costs	0.0	0.0
Interest costs	0.0	0.0
Expected return on plan assets	0.0	0.0
Recognized net actuarial loss	0.1	0.1
Net periodic benefit (income) expense	$ 0.1	$ 0.1