Pension and Other Postretirement Benefits (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Pension and other postretirement benefits
Payment for unfunded pension plans			$ 1.0
Pension Benefits
Pension and other postretirement benefits
Defined benefit plan investments	$ 1.8		1.8
Defined benefit plan investments classified as prepaid and other current assets	0.6		0.6
Defined benefit plan investments classified as other assets	1.2		1.2
Service cost	1.4	$ 1.4	2.9	$ 2.7
Interest cost	3.3	3.9	6.7	7.7
Expected return on plan assets	(4.5)	(4.2)	(9.1)	(8.4)
Recognized net actuarial loss	1.7	1.0	3.4	2.1
Amortization of prior service cost (benefit)			0.1	0.1
Net periodic benefit cost	1.9	2.1	4.0	4.2
Aggregate contributions to qualified and non-qualified pension trusts and payments of pension benefits for unfunded pension plans			7.0
Postretirement Benefits Other than Pensions
Pension and other postretirement benefits
Service cost	0.5	0.4	0.8	0.8
Interest cost	0.4	0.5	0.8	1.0
Recognized net actuarial loss	0.1	0.1	0.1	0.1
Amortization of prior service cost (benefit)	(0.1)	(0.1)	(0.1)	(0.1)
Net periodic benefit cost	$ 0.9	$ 0.9	$ 1.6	$ 1.8