Accumulated Other Comprehensive Income Loss (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Oct. 31, 2015	Oct. 31, 2014	Oct. 31, 2015		Oct. 31, 2014
Accumulated Other Comprehensive Loss [Line Items]
Accumulated Other Comprehensive Loss, Beginning Balance				$ (109.8)		$ (51.6)
Reclassification adjustments				7.6		(14.5)
Current period (charge) credit				(25.0)		(12.9)
Income tax benefit (expense)				(1.6)		4.8
Accumulated Other Comprehensive Loss, Ending Balance		$ (128.8)	$ (74.2)	(128.8)		(74.2)
Cost of Products Sold [Member] | Commodity contracts [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) reclassified from accumulated other comprehensive loss to earnings (effective portion)		0.0	11.8	0.0		18.8
Interest Expense [Member] | Interest rate contract [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) reclassified from accumulated other comprehensive loss to earnings (effective portion)		(0.2)	(0.2)	(0.3)		(0.3)
Foreign Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Loss [Line Items]
Accumulated Other Comprehensive Loss, Beginning Balance				(2.3)		31.7
Reclassification adjustments				0.0		0.0
Current period (charge) credit				(22.9)		(14.4)
Income tax benefit (expense)				0.0		0.0
Accumulated Other Comprehensive Loss, Ending Balance		(25.2)	17.3	(25.2)		17.3
Unrealized (Loss) Gain on Cash Flow Hedging Derivatives [Member]
Accumulated Other Comprehensive Loss [Line Items]
Accumulated Other Comprehensive Loss, Beginning Balance	[1]			(5.2)		15.3
Reclassification adjustments	[1]			0.3		(18.5)
Current period (charge) credit	[1]			0.0		0.0
Income tax benefit (expense)	[1]			(0.1)		6.8
Accumulated Other Comprehensive Loss, Ending Balance	[1]	(5.0)	3.6	(5.0)		3.6
Pension and Other Postretirement Liabilities [Member]
Accumulated Other Comprehensive Loss [Line Items]
Accumulated Other Comprehensive Loss, Beginning Balance	[2]			(105.6)		(102.0)
Reclassification adjustments		(2.5)	(1.8)	7.3	[2]	4.0	[2]
Current period (charge) credit	[2]			(1.5)		0.6
Income tax benefit (expense)	[2]			(1.7)		(1.7)
Accumulated Other Comprehensive Loss, Ending Balance	[2]	(101.5)	(99.1)	(101.5)		(99.1)
Unrealized Gain on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Loss [Line Items]
Accumulated Other Comprehensive Loss, Beginning Balance				3.3		3.4
Reclassification adjustments				0.0		0.0
Current period (charge) credit				(0.6)		0.9
Income tax benefit (expense)				0.2		(0.3)
Accumulated Other Comprehensive Loss, Ending Balance		$ 2.9	$ 4.0	$ 2.9		$ 4.0

[1] Of the total losses reclassified from accumulated other comprehensive loss, $0.2 of expense was reclassified to interest expense related to the terminated interest rate swap for the three months ended October 31, 2015 and 2014, and $0.3 of expense was reclassified for the six months ended October 31, 2015 and 2014. Of the total losses reclassified from accumulated other comprehensive loss, $11.8 and $18.8 of income was reclassified to cost of products sold related to commodity derivatives for the three and six months ended October 31, 2014, respectively.

[2] Of the total amortization of net losses reclassified from accumulated other comprehensive loss to selling, distribution, and administrative expense for the six months ended October 31, 2015 and 2014, $2.5 and $1.8 was reclassified for the three months ended October 31, 2015 and 2014, respectively.