Pension and Postretirement Benefits (Components of net periodic benefit) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Pension Benefits
Components of net periodic benefit cost
Service costs	$ 0.9	$ 0.6	$ 2.9	$ 1.9
Interest costs	0.6	0.4	1.7	1.3
Expected return on plan assets	(2.9)	(2.4)	(8.7)	(7.2)
Recognized net actuarial loss	0.1	0.3	0.3	0.9
Net periodic benefit (income) costs	(1.3)	(1.1)	$ (3.8)	$ (3.1)
Weighted average:
Discount rate for PBO			3.51%	3.91%
Discount rate for interest cost			3.08%	3.20%
Discount rate for service cost			3.60%	3.98%
Expected return on plan assets			8.25%	8.25%
Postretirement Benefits
Components of net periodic benefit cost
Service costs	0.0	0.0	$ 0.0	$ 0.0
Interest costs	0.1	0.1	0.2	0.2
Expected return on plan assets	0.0	0.0	0.0	0.0
Recognized net actuarial loss	0.1	0.0	0.1	0.1
Net periodic benefit (income) costs	$ 0.2	$ 0.1	$ 0.3	$ 0.3
Weighted average:
Discount rate for PBO			3.32%	3.63%
Discount rate for interest cost			2.89%	2.92%
Discount rate for service cost			3.70%	4.12%