Pension and Postretirement Benefits (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer	$ 1.8	$ 2.6	$ 3.4	$ 4.8
Pension [Member]
Pension and postretirement benefit plans [Abstract]
Service cost	0.2	0.2	0.3	0.3
Interest cost	3.3	3.4	6.5	6.7
Expected return on plan assets	(4.0)	(4.0)	(7.9)	(8.0)
Amortization of [Abstract]
Unrecognized net loss	1.5	1.2	3.1	2.5
Unrecognized prior service credit	0	0	0	0
Net periodic benefit cost (income)	1.0	0.8	2.0	1.5
Postretirement [Member]
Pension and postretirement benefit plans [Abstract]
Service cost	0	0	0	0
Interest cost	0	0.1	0.1	0.2
Expected return on plan assets	0	0	0	0
Amortization of [Abstract]
Unrecognized net loss	0	0	0	0
Unrecognized prior service credit	(0.3)	(0.4)	(0.6)	(0.8)
Net periodic benefit cost (income)	$ (0.3)	$ (0.3)	$ (0.5)	$ (0.6)