Stock-Based Compensation (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Feb. 28, 2019	Feb. 28, 2018	Feb. 28, 2019	Feb. 28, 2018
Stock-Based Compensation (Details) - Schedule of stock-based compensation [Line Items]
Stock-based compensation expense	$ 1.6	$ 1.6	$ 6.8	$ 9.1
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period	0.1	0.2	0.4	0.4
Stock option expense
Stock-Based Compensation (Details) - Schedule of stock-based compensation [Line Items]
Stock-based compensation expense	$ 0.7	$ 0.8	$ 4.3	$ 6.2
Restricted stock unit expense
Stock-Based Compensation (Details) - Schedule of stock-based compensation [Line Items]
Stock-based compensation expense	0.7	0.6	2.0	2.0
Management stock purchase plan
Stock-Based Compensation (Details) - Schedule of stock-based compensation [Line Items]
Stock-based compensation expense	0.0	0.1	0.2	0.7
Employee stock purchase plan
Stock-Based Compensation (Details) - Schedule of stock-based compensation [Line Items]
Stock-based compensation expense	$ 0.2	$ 0.1	$ 0.3	$ 0.2