Consolidated Statement of Changes in Stockholders’ Equity - USD ($) shares in Millions, $ in Millions	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Treasury Stock At Cost [Member]	Class A Stock [Member] Common Stock [Member]
Balance at May. 31, 2015	$ 1,204.9	$ 0.4	$ 591.5	$ (77.0)	$ 1,039.9	$ (349.9)	$ 0.0
Balance (in Shares) at May. 31, 2015		31.5					1.7
Net Income (loss)	40.5				40.5
Foreign currency translation adjustment	(8.1)			(8.1)
Pension and postretirement adjustments, net of tax	(1.6)			(1.6)
Stock-based compensation	9.7		9.7
Proceeds pursuant to stock-based compensation plans	47.2		47.2
Proceeds from issuance of common stock pursuant to stock-based compensation (in Shares)		0.0
Purchases of treasury stock at cost	(14.4)					(14.4)
Purchases of treasury stock at cost (in Shares)		(0.4)
Treasury stock issued pursuant to equity-based plans	0.0		(47.7)			47.7
Treasury stock issued pursuant to stock purchase plans (in Shares)		1.6
Dividends	(20.6)				(20.6)
Balance at May. 31, 2016	1,257.6	$ 0.4	600.7	(86.7)	1,059.8	(316.6)	$ 0.0
Balance (in Shares) at May. 31, 2016		32.7					1.7
Net Income (loss)	52.3				52.3
Foreign currency translation adjustment	(5.3)			(5.3)
Pension and postretirement adjustments, net of tax	(2.2)			(2.2)
Stock-based compensation	10.1		10.1
Proceeds pursuant to stock-based compensation plans	22.5		22.5
Proceeds from issuance of common stock pursuant to stock-based compensation (in Shares)		0.0
Purchases of treasury stock at cost	(6.9)					(6.9)
Purchases of treasury stock at cost (in Shares)		(0.2)
Treasury stock issued pursuant to equity-based plans	0.7		(26.5)			27.2
Treasury stock issued pursuant to stock purchase plans (in Shares)		0.9
Dividends	(20.9)				(20.9)
Balance at May. 31, 2017	1,307.9	$ 0.4	606.8	(94.2)	1,091.2	(296.3)	$ 0.0
Balance (in Shares) at May. 31, 2017		33.4					1.7
Net Income (loss)	(5.0)				(5.0)
Foreign currency translation adjustment	3.4			3.4
Pension and postretirement adjustments, net of tax	35.1			35.1
Stock-based compensation	10.7		10.7
Proceeds pursuant to stock-based compensation plans	15.8		15.8
Proceeds from issuance of common stock pursuant to stock-based compensation (in Shares)		0.0
Purchases of treasury stock at cost	$ (27.2)					(27.2)
Purchases of treasury stock at cost (in Shares)	(0.7)	(0.7)
Treasury stock issued pursuant to equity-based plans	$ 1.1		(18.9)			20.0
Treasury stock issued pursuant to stock purchase plans (in Shares)		0.6
Dividends	(21.0)				(21.0)
Balance at May. 31, 2018	$ 1,320.8	$ 0.4	$ 614.4	$ (55.7)	$ 1,065.2	$ (303.5)	$ 0.0
Balance (in Shares) at May. 31, 2018		33.3					1.7