Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Feb. 29, 2012	May 31, 2013	May 31, 2012 item	May 31, 2011
Current:
Federal		$ (13.1)	$ (9.8)	$ (8.6)
State		(1.8)	(0.5)	1.5
Foreign		12.1	3.0	1.8
Total current		(2.8)	(7.3)	(5.3)
Deferred		29.5	32.8	38.9
Provision for income taxes		26.7	25.5	33.6
Income tax receivable		18.0	22.8
U.S. federal statutory income tax rate (as a percent)		35.00%	35.00%	35.00%
Reasons for difference between the provision for income taxes on pre-tax income from the amount computed by applying the U.S. federal statutory tax rate
Provision for income taxes at the federal statutory rate		28.8	32.7	36.2
State income taxes, net of federal benefit and refunds	4.0	(1.0)	(3.5)	0.9
Research and development credit		(1.1)	(0.8)	(0.4)
Noncontrolling interest		(0.2)	(0.1)
Settlement of tax examinations				(3.5)
Federal adjustments			(3.3)
Other		0.2	0.5	0.4
Provision for income taxes		26.7	25.5	33.6
Deferred tax assets-current attributable to:
Inventory costs		14.8	11.3
Employee benefits		8.3	6.0
Allowance for doubtful accounts		1.6	2.1
AMT, NOL and FTC carrybacks			7.3
Advanced billings and other		(6.7)	(4.1)
Total net deferred tax assets-current		18.0	22.6
Deferred tax assets-noncurrent attributable to:
Postretirement benefits		17.7	19.6
Bond hedge		1.7	3.1
Foreign intangible assets		41.5	39.5
AMT, NOL and FTC carrybacks		37.6
Other		1.0	4.8
Total deferred tax assets-noncurrent		99.5	67.0
Total deferred tax assets		117.5	89.6
Deferred tax liabilities attributable to:
Depreciation		(163.5)	(119.0)
Convertible notes		(3.9)	(7.0)
Capitalized program development costs		(28.8)	(17.3)
Foreign intangible assets		(41.5)	(39.6)
Total deferred tax liabilities		(237.7)	(182.9)
Net deferred tax liabilities		(120.2)	(93.3)
Effective income tax rate (as a percent)		32.50%	27.20%
Number of significant businesses relocated			1
Unrecognized tax benefits		0
Reduction in income tax expense primarily due to allowance of foreign tax credits which had not been previously benefited				(3.5)
Reduction in income tax expense related to reduction of the entity's state income tax rate		$ 1.3	$ 4.0