Accumulated Other Comprehensive Loss (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Mar. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (128.4)
Other comprehensive income before reclassifications	28.2
Reclassifications [Abstract]
Tax benefit (expense)	(9.2)
Total other comprehensive income (loss)	24.5
Ending balance	(103.9)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassifications [Abstract]
Amortization of unrecognized net loss	6.2	[1]
Amortization of unrecognized prior service credit	(1.2)	[1]
Commodity derivatives	0.5	[2]
Foreign Currency Translation [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	17.8
Other comprehensive income before reclassifications	9.5
Reclassifications [Abstract]
Tax benefit (expense)	0
Total other comprehensive income (loss)	9.5
Ending balance	27.3
Foreign Currency Translation [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassifications [Abstract]
Amortization of unrecognized net loss	0	[1]
Amortization of unrecognized prior service credit	0	[1]
Commodity derivatives	0	[2]
Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(1.1)
Other comprehensive income before reclassifications	0
Reclassifications [Abstract]
Tax benefit (expense)	0.6
Total other comprehensive income (loss)	1.1
Ending balance	0
Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassifications [Abstract]
Amortization of unrecognized net loss	0	[1]
Amortization of unrecognized prior service credit	0	[1]
Commodity derivatives	0.5	[2]
Defined Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(145.1)
Other comprehensive income before reclassifications	18.7
Reclassifications [Abstract]
Tax benefit (expense)	(9.8)
Total other comprehensive income (loss)	13.9
Ending balance	(131.2)
Defined Benefit Plans [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassifications [Abstract]
Amortization of unrecognized net loss	6.2	[1]
Amortization of unrecognized prior service credit	(1.2)	[1]
Commodity derivatives	$ 0	[2]

[1] Amounts are included in the calculation of net periodic benefit cost. See Note 17 for additional information.

[2] Reclassifications for commodity derivatives are included in cost of sales.