Stock-Based Compensation (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Feb. 28, 2021	Feb. 29, 2020	Feb. 28, 2021	Feb. 29, 2020
Stock-Based Compensation (Details) - Schedule of stock-based compensation [Line Items]
Stock-based compensation expense	$ 1.5	$ 0.7	$ 5.1	$ 3.1
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period	0.1	0.0	0.2	0.1
Stock option expense
Stock-Based Compensation (Details) - Schedule of stock-based compensation [Line Items]
Stock-based compensation expense	$ 0.7	$ 0.4	$ 3.5	$ 1.4
Restricted stock unit expense
Stock-Based Compensation (Details) - Schedule of stock-based compensation [Line Items]
Stock-based compensation expense	0.7	0.3	1.4	1.5
Management stock purchase plan
Stock-Based Compensation (Details) - Schedule of stock-based compensation [Line Items]
Stock-based compensation expense	0.0	0.0	0.0	0.0
Employee stock purchase plan
Stock-Based Compensation (Details) - Schedule of stock-based compensation [Line Items]
Stock-based compensation expense	$ 0.1	$ 0.0	$ 0.2	$ 0.2