CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY Statement - USD ($) $ in Millions	Total	Common Stock	Common Stock Common Class A	Additional Paid-in Capital [Member]	AOCI Attributable to Parent [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Parent [Member]	Noncontrolling Interest [Member]
Beginning balance at May. 31, 2019	$ 1,272.8	$ 0.4	$ 0.0	$ 620.8	$ (59.7)	$ 1,012.6	$ (302.6)	$ 1,271.5	$ 1.3
Balance (in shares) at Aug. 31, 2019		33,100,000	1,700,000
Net Income (loss)	(58.5)					(58.5)		(58.5)	0.0
Foreign currency translation adjustment	(2.0)				(2.0)			(2.0)
Pension and post-retirement adjustments (net of tax of $0.0)	0.2				0.2			0.2
Stock-based compensation	1.5			1.5				1.5
Purchases of treasury stock at cost (in shares)		(300,000)
Purchases of treasury stock at cost	(12.6)						(12.6)	(12.6)
Treasury stock issued pursuant to equity-based plans (in shares)		0.0
Treasury stock issued pursuant to equity-based plans	0.5			(0.1)			0.6	0.5
Dividends ($0.15 per share)	(5.2)					(5.2)		(5.2)
Ending Balance at Aug. 31, 2019	1,196.7	$ 0.4	$ 0.0	622.2	(61.5)	948.9	(314.6)	1,195.4	1.3
Balance (in shares) at May. 31, 2019		33,400,000	1,700,000
Beginning balance at May. 31, 2019	1,272.8	$ 0.4	$ 0.0	620.8	(59.7)	1,012.6	(302.6)	1,271.5	1.3
Balance (in shares) at Feb. 29, 2020		32,600,000	1,700,000
Foreign currency translation adjustment	(0.4)
Ending Balance at Feb. 29, 2020	1,199.3	$ 0.4	$ 0.0	621.9	(59.4)	966.2	(331.2)	1,197.9	1.4
Balance (in shares) at May. 31, 2019		33,400,000	1,700,000
Beginning balance at Aug. 31, 2019	1,196.7	$ 0.4	$ 0.0	622.2	(61.5)	948.9	(314.6)	1,195.4	1.3
Balance (in shares) at Nov. 30, 2019		33,000,000.0	1,700,000
Net Income (loss)	71.0					71.0		71.0	0.0
Foreign currency translation adjustment	3.9				3.9			3.9
Pension and post-retirement adjustments (net of tax of $0.0)	0.2				0.2			0.2
Stock-based compensation	0.9			0.9				0.9
Proceeds pursuant to stock-based compensation plans	0.3			0.3				0.3
Purchases of treasury stock at cost (in shares)		(100,000)
Purchases of treasury stock at cost	(7.1)						(7.1)	(7.1)
Treasury stock issued pursuant to equity-based plans (in shares)		0.0
Treasury stock issued pursuant to equity-based plans	0.6			(2.1)			2.7	0.6
Dividends ($0.15 per share)	(5.2)					(5.2)		(5.2)
Ending Balance at Nov. 30, 2019	1,261.3	$ 0.4	$ 0.0	621.3	(57.4)	1,014.7	(319.0)	1,260.0	1.3
Balance (in shares) at Aug. 31, 2019		33,100,000	1,700,000
Balance (in shares) at Feb. 29, 2020		32,600,000	1,700,000
Net Income (loss)	(43.2)					(43.3)		(43.3)	0.1
Foreign currency translation adjustment	(2.3)				(2.3)			(2.3)
Pension and post-retirement adjustments (net of tax of $0.0)	0.3				0.3			0.3
Stock-based compensation	0.7			0.7				0.7
Proceeds pursuant to stock-based compensation plans	0.4			0.4				0.4
Purchases of treasury stock at cost (in shares)		(400,000)
Purchases of treasury stock at cost	(13.0)						(13.0)	(13.0)
Treasury stock issued pursuant to equity-based plans (in shares)		0.0
Treasury stock issued pursuant to equity-based plans	0.3			(0.5)			0.8	0.3
Dividends ($0.15 per share)	(5.2)					(5.2)		(5.2)
Ending Balance at Feb. 29, 2020	1,199.3	$ 0.4	$ 0.0	621.9	(59.4)	966.2	(331.2)	1,197.9	1.4
Balance (in shares) at Nov. 30, 2019		33,000,000.0	1,700,000
Beginning balance at May. 31, 2020	1,180.6	$ 0.4	$ 0.0	622.4	(58.3)	948.0	(333.3)	1,179.2	1.4
Balance (in shares) at Aug. 31, 2020		32,500,000	1,700,000
Net Income (loss)	(39.8)					(39.8)		(39.8)	0.0
Foreign currency translation adjustment	10.7				10.7			10.7
Pension and post-retirement adjustments (net of tax of $0.0)	0.1				0.1			0.1
Stock-based compensation	0.6			0.6				0.6
Treasury stock issued pursuant to equity-based plans (in shares)		0.0
Treasury stock issued pursuant to equity-based plans	0.3			(0.2)			0.5	0.3
Dividends ($0.15 per share)	(5.1)					(5.1)		(5.1)
Ending Balance at Aug. 31, 2020	1,147.4	$ 0.4	$ 0.0	622.8	(47.5)	903.1	(332.8)	1,146.0	1.4
Balance (in shares) at May. 31, 2020		32,500,000	1,700,000
Beginning balance at May. 31, 2020	1,180.6	$ 0.4	$ 0.0	622.4	(58.3)	948.0	(333.3)	1,179.2	1.4
Balance (in shares) at Feb. 28, 2021		32,700,000	1,700,000
Foreign currency translation adjustment	$ 17.4
Purchases of treasury stock at cost (in shares)	0
Ending Balance at Feb. 28, 2021	$ 1,176.8	$ 0.4	$ 0.0	625.4	(35.4)	913.9	(328.9)	1,175.4	1.4
Balance (in shares) at May. 31, 2020		32,500,000	1,700,000
Beginning balance at Aug. 31, 2020	1,147.4	$ 0.4	$ 0.0	622.8	(47.5)	903.1	(332.8)	1,146.0	1.4
Balance (in shares) at Nov. 30, 2020		32,600,000	1,700,000
Net Income (loss)	35.2					35.1		35.1	0.1
Foreign currency translation adjustment	0.4				0.4	0.0		0.4
Pension and post-retirement adjustments (net of tax of $0.0)	5.4				5.4			5.4
Stock-based compensation	3.0			3.0				3.0
Treasury stock issued pursuant to equity-based plans (in shares)		100,000
Treasury stock issued pursuant to equity-based plans	1.6			(1.5)			3.1	1.6
Dividends ($0.15 per share)	(5.1)					(5.1)		(5.1)
Ending Balance at Nov. 30, 2020	1,187.9	$ 0.4	$ 0.0	624.3	(41.7)	933.1	(329.7)	1,186.4	1.5
Balance (in shares) at Aug. 31, 2020		32,500,000	1,700,000
Balance (in shares) at Feb. 28, 2021		32,700,000	1,700,000
Net Income (loss)	(14.0)					(13.9)		(13.9)	(0.1)
Foreign currency translation adjustment	6.3				6.3			6.3
Pension and post-retirement adjustments (net of tax of $0.0)	0.0				0.0			0.0
Stock-based compensation	$ 1.5			1.5				1.5
Purchases of treasury stock at cost (in shares)	0
Treasury stock issued pursuant to equity-based plans (in shares)		100,000
Treasury stock issued pursuant to equity-based plans	$ 0.4			(0.4)			0.8	0.4
Dividends ($0.15 per share)	(5.3)					(5.3)		(5.3)
Ending Balance at Feb. 28, 2021	$ 1,176.8	$ 0.4	$ 0.0	$ 625.4	$ (35.4)	$ 913.9	$ (328.9)	$ 1,175.4	$ 1.4
Balance (in shares) at Nov. 30, 2020		32,600,000	1,700,000