Condensed Consolidated Statements of Changes in Equity - USD ($) $ in Millions	Common Stock	Capital Surplus	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Total
Balance at May. 31, 2021	$ 45.3	$ 479.8	$ 741.7	$ (274.1)	$ (18.3)	$ 974.4
Increase (Decrease) in Stockholders' Equity
Net income			11.5			11.5
Stock option activity		1.1		0.2		1.3
Restricted stock activity		(1.0)		2.3		1.3
Other comprehensive income (loss), net of tax					(0.3)	(0.3)
Balance at Aug. 31, 2021	45.3	479.9	753.2	(271.6)	(18.6)	988.2
Balance at May. 31, 2021	45.3	479.8	741.7	(274.1)	(18.3)	974.4
Increase (Decrease) in Stockholders' Equity
Net income						54.8
Other comprehensive income (loss), net of tax						(1.8)
Balance at Feb. 28, 2022	45.3	481.4	796.5	(285.4)	(20.1)	1,017.7
Balance at Aug. 31, 2021	45.3	479.9	753.2	(271.6)	(18.6)	988.2
Increase (Decrease) in Stockholders' Equity
Net income			20.8			20.8
Stock option activity		0.9				0.9
Restricted stock activity		0.7				0.7
Other comprehensive income (loss), net of tax					(3.6)	(3.6)
Balance at Nov. 30, 2021	45.3	481.5	774.0	(271.6)	(22.2)	1,007.0
Increase (Decrease) in Stockholders' Equity
Net income			22.5			22.5
Stock option activity		(0.4)		6.4		6.0
Restricted stock activity		0.3				0.3
Repurchase of shares				(20.2)		(20.2)
Other comprehensive income (loss), net of tax					2.1	2.1
Balance at Feb. 28, 2022	45.3	481.4	796.5	(285.4)	(20.1)	1,017.7
Balance at May. 31, 2022	45.3	477.5	820.4	(289.1)	(19.6)	1,034.5
Increase (Decrease) in Stockholders' Equity
Net income			22.7			22.7
Stock option activity		1.0		1.5		2.5
Restricted stock activity		(1.7)		3.5		1.8
Repurchase of shares				(21.9)		(21.9)
Other comprehensive income (loss), net of tax					(3.1)	(3.1)
Balance at Aug. 31, 2022	45.3	476.8	843.1	(306.0)	(22.7)	1,036.5
Balance at May. 31, 2022	45.3	477.5	820.4	(289.1)	(19.6)	1,034.5
Increase (Decrease) in Stockholders' Equity
Net income						67.0
Other comprehensive income (loss), net of tax						(2.4)
Balance at Feb. 28, 2023	45.3	481.2	887.4	(324.2)	(22.0)	1,067.7
Balance at Aug. 31, 2022	45.3	476.8	843.1	(306.0)	(22.7)	1,036.5
Increase (Decrease) in Stockholders' Equity
Net income			22.5			22.5
Stock option activity		0.2		2.4		2.6
Restricted stock activity		2.0				2.0
Repurchase of shares				(28.2)		(28.2)
Other comprehensive income (loss), net of tax					(0.1)	(0.1)
Balance at Nov. 30, 2022	45.3	479.0	865.6	(331.8)	(22.8)	1,035.3
Increase (Decrease) in Stockholders' Equity
Net income			21.8			21.8
Stock option activity		(0.5)		7.7		7.2
Restricted stock activity		2.7		(0.1)		2.6
Other comprehensive income (loss), net of tax					0.8	0.8
Balance at Feb. 28, 2023	$ 45.3	$ 481.2	$ 887.4	$ (324.2)	$ (22.0)	$ 1,067.7