CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Millions	Common Stock	Capital Surplus	Retained Earnings Cumulative effect adjustment	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Total Equity Cumulative effect adjustment	Total Equity	Total
Balance (ASC 606) at May. 31, 2018			$ (20.4)				$ (20.4)
Balance at May. 31, 2018	$ 45.3	$ 470.5		$ 733.2	$ (280.7)	$ (32.0)		$ 936.3
Increase (Decrease) in Stockholders' Equity
Net income				7.5				7.5	$ 7.5
Cash dividends				(10.5)				(10.5)
Stock option activity		3.5			4.1			7.6
Restricted stock activity		5.4			(0.8)			4.6
Repurchase of shares					(10.3)			(10.3)
Other comprehensive income (loss), net of tax						(8.9)		(8.9)	(8.9)
Balance (ASC 842) at May. 31, 2019			$ 2.5				$ 2.5
Balance at May. 31, 2019	45.3	479.4		709.8	(287.7)	(40.9)		905.9
Increase (Decrease) in Stockholders' Equity
Net income				4.4				4.4	4.4
Cash dividends				(10.7)				(10.7)
Stock option activity		3.1			8.3			11.4
Restricted stock activity		(3.9)			0.8			(3.1)
Repurchase of shares					(4.1)			(4.1)
Other comprehensive income (loss), net of tax						(3.7)		(3.7)	(3.7)
Balance at May. 31, 2020	45.3	478.6		706.0	(282.7)	(44.6)		902.6	902.6
Increase (Decrease) in Stockholders' Equity
Net income				35.8				35.8	35.8
Cash dividends				(0.1)				(0.1)
Stock option activity		3.6			3.0			6.6
Restricted stock activity		(2.4)			5.6			3.2
Repurchase of shares					(5.6)
Other comprehensive income (loss), net of tax						26.3		26.3	26.3
Balance at May. 31, 2021	$ 45.3	$ 479.8		$ 741.7	$ (274.1)	$ (18.3)		$ 974.4	$ 974.4