Pension and Postretirement Benefits (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer	$ 2.8	$ 2.8	$ 6.2	$ 7.6
Pension [Member]
Pension and postretirement benefit plans [Abstract]
Service cost	0.2	0.1	0.5	0.5
Interest cost	3.2	3.4	9.7	10.1
Expected return on plan assets	(3.9)	(4.0)	(11.8)	(12.1)
Amortization of [Abstract]
Unrecognized net loss	1.6	1.2	4.7	3.7
Unrecognized prior service credit	0	0	0	0
Net periodic benefit cost (income)	1.1	0.7	3.1	2.2
Postretirement [Member]
Pension and postretirement benefit plans [Abstract]
Service cost	0	0	0	0
Interest cost	0.1	0.1	0.2	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)	(0.9)	(1.1)
Net periodic benefit cost (income)	$ (0.2)	$ (0.3)	$ (0.7)	$ (0.9)