Pension Plans and Other Postretirement Benefits (Components of net periodic benefit) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Pension Benefits
Components of net periodic benefit cost
Service costs	$ 0.6	$ 0.6	$ 1.2	$ 1.2
Interest costs	0.4	0.6	0.9	1.2
Expected return on plan assets	(2.4)	(2.5)	(4.8)	(5.0)
Recognized net actuarial loss	0.3	0.0	0.6	0.0
Net periodic benefit (income) costs	(1.1)	(1.3)	(2.1)	(2.6)
Other Postretirement Benefits (OPEB)
Components of net periodic benefit cost
Service costs	0.0	0.0	0.0	0.0
Interest costs	0.1	0.2	0.2	0.3
Expected return on plan assets	0.0	0.0	0.0	0.0
Recognized net actuarial loss	0.1	0.1	0.2	0.3
Net periodic benefit (income) costs	$ 0.2	$ 0.3	$ 0.4	$ 0.6