Pension and Postretirement Benefits (Components of net periodic benefit) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Pension Benefits
Components of net periodic benefit cost
Service costs	$ 0.7	$ 0.6	$ 1.3	$ 1.2
Interest costs	0.4	0.4	0.9	0.9
Expected return on plan assets	(2.4)	(2.4)	(4.8)	(4.8)
Recognized net actuarial loss	0.3	0.3	0.6	0.6
Net periodic benefit (income) costs	(1.0)	(1.1)	$ (2.0)	$ (2.1)
Weighted average:
Discount rate, weighted average			3.91%	4.13%
Expected return on plan assets, weighted average			8.25%	8.25%
Postretirement Benefits
Components of net periodic benefit cost
Service costs	0.0	0.0	$ 0.0	$ 0.0
Interest costs	0.0	0.1	0.1	0.2
Expected return on plan assets	0.0	0.0	0.0	0.0
Recognized net actuarial loss	0.1	0.1	0.1	0.2
Net periodic benefit (income) costs	$ 0.1	$ 0.2	$ 0.2	$ 0.4
Weighted average:
Discount rate, weighted average			3.63%	3.80%