Pension and Postretirement Benefits (Components of net periodic benefit) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Pension Benefits
Components of net periodic benefit cost
Service costs	$ 1.1	$ 1.1	$ 2.2	$ 2.2
Interest costs	0.4	0.6	0.7	1.1
Expected return on plan assets	(3.1)	(2.9)	(6.2)	(5.8)
Recognized net actuarial loss	0.2	0.5	0.4	1.0
Net periodic benefit (income) expense	(1.4)	(0.7)	(2.9)	(1.5)
Postretirement Benefits
Components of net periodic benefit cost
Service costs	0.0	0.0	0.0	0.0
Interest costs	0.1	0.1	0.1	0.1
Expected return on plan assets	0.0	0.0	0.0	0.0
Recognized net actuarial loss	0.1	0.0	0.2	0.1
Net periodic benefit (income) expense	$ 0.2	$ 0.1	$ 0.3	$ 0.2