Consolidated Statement of Changes in Stockholders' Equity and Comprehensive Income (Loss) (USD $) In Millions, except Share data, unless otherwise specified	Common Class A [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Total
Balance at May. 31, 2009	$ 0	$ 0.4	$ 552.9	$ (77.1)	$ 562.8	$ (254.0)	$ 785.0
Balance (in Shares) at May. 31, 2009	1,656,200	34,740,275
Comprehensive income (loss):
Net Income (loss)					56.1		56.1
Other comprehensive income (loss), net:
Foreign currency translation adjustment				2.8			2.8
Pension and postretirement adjustments, net of tax				(11.1)			(11.1)
Total other comprehensive income (loss)							(8.3)
Total comprehensive income (loss)							47.8
Stock-based compensation			14.0				14.0
Proceeds from issuance of common stock pursuant to stock-based compensation			3.2				3.2
Proceeds from issuance of common stock pursuant to stock-based compensation (in Shares)		134,045
Purchases of treasury stock at cost						(10.8)	(10.8)
Purchases of treasury stock at cost (in Shares)		(411,977)
Treasury stock issued pursuant to stock purchase plans			(0.9)			3.2	2.3
Treasury stock issued pursuant to stock purchase plans (in Shares)		135,915
Dividends					(11.1)		(11.1)
Balance at May. 31, 2010	0	0.4	569.2	(85.4)	607.8	(261.6)	830.4
Balance (in Shares) at May. 31, 2010	1,656,200	34,598,258
Comprehensive income (loss):
Net Income (loss)					39.4		39.4
Other comprehensive income (loss), net:
Foreign currency translation adjustment				25.2			25.2
Pension and postretirement adjustments, net of tax				6.3			6.3
Total other comprehensive income (loss)							31.5
Total comprehensive income (loss)							70.9
Stock-based compensation			13.7				13.7
Proceeds from issuance of common stock pursuant to stock-based compensation			2.9				2.9
Proceeds from issuance of common stock pursuant to stock-based compensation (in Shares)		104,100
Purchases of treasury stock at cost						(166.9)	(166.9)
Purchases of treasury stock at cost (in Shares)		(5,588,125)
Treasury stock issued pursuant to stock purchase plans			(9.2)			9.6	0.4
Treasury stock issued pursuant to stock purchase plans (in Shares)		202,458
Dividends					(11.4)		(11.4)
Balance at May. 31, 2011	0	0.4	576.6	(53.9)	635.8	(418.9)	740.0
Balance (in Shares) at May. 31, 2011	1,656,200	29,316,691
Comprehensive income (loss):
Net Income (loss)					102.4		102.4
Other comprehensive income (loss), net:
Foreign currency translation adjustment				(8.2)			(8.2)
Pension and postretirement adjustments, net of tax				(12.1)			(12.1)
Total other comprehensive income (loss)							(20.3)
Total comprehensive income (loss)							82.1
Stock-based compensation			12.2				12.2
Proceeds from issuance of common stock pursuant to stock-based compensation			22.4				22.4
Proceeds from issuance of common stock pursuant to stock-based compensation (in Shares)		724,613
Purchases of treasury stock at cost						(13.1)	(13.1)
Purchases of treasury stock at cost (in Shares)		(475,672)
Treasury stock issued pursuant to stock purchase plans			(28.2)			29.2	1.0
Treasury stock issued pursuant to stock purchase plans (in Shares)		230,279
Dividends					(14.3)		(14.3)
Balance at May. 31, 2012	$ 0	$ 0.4	$ 583.0	$ (74.2)	$ 723.9	$ (402.8)	$ 830.3
Balance (in Shares) at May. 31, 2012	1,656,200	29,795,911