Employee Benefit Plans - Reconciliation of Pension Assets (Details) - Defined Benefit Pension Plans - USD ($) $ in Millions	May 31, 2023	May 31, 2022	May 31, 2021
Employee benefit plans
Fair value of plan assets	$ 112.6	$ 126.2	$ 158.4
Government securities and corporate bond mutual funds | Total
Employee benefit plans
Fair value of plan assets	60.0	49.6
Funds-of-funds | Total
Employee benefit plans
Fair value of plan assets	39.9	45.9
Insurance Annuities | Total
Employee benefit plans
Fair value of plan assets	10.4	11.3
Cash and cash equivalents | Total
Employee benefit plans
Fair value of plan assets	2.3	14.6
Total Investments | Total
Employee benefit plans
Fair value of plan assets	112.6	121.4
Total pension plan assets | Total
Employee benefit plans
Fair value of plan assets		126.2
Quoted prices in active markets (Level 1) | Cash and cash equivalents
Employee benefit plans
Fair value of plan assets	2.3	14.6
Quoted prices in active markets (Level 1) | Total Investments
Employee benefit plans
Fair value of plan assets	2.3	14.6
Significant other observable inputs (Level 2) | Government securities and corporate bond mutual funds
Employee benefit plans
Fair value of plan assets	60.0	49.6
Significant other observable inputs (Level 2) | Funds-of-funds
Employee benefit plans
Fair value of plan assets	39.9	45.9
Significant other observable inputs (Level 2) | Total Investments
Employee benefit plans
Fair value of plan assets	99.9	95.5
Significant other unobservable inputs (Level 3) | Insurance Annuities
Employee benefit plans
Fair value of plan assets	10.4	11.3	$ 15.6
Significant other unobservable inputs (Level 3) | Total Investments
Employee benefit plans
Fair value of plan assets	$ 10.4	11.3
Measured at net asset value | Other investments measured at net asset value | Total
Employee benefit plans
Fair value of plan assets		$ 4.8