Employee Benefit Plans - Reconciliation of Pension Assets (Details) - Defined Benefit Pension Plans - USD ($) $ in Millions	May 31, 2022	May 31, 2021	May 31, 2020
Employee benefit plans
Fair value of plan assets	$ 126.2	$ 158.4	$ 131.8
U.S. mutual funds | Total
Employee benefit plans
Fair value of plan assets		40.3
International mutual funds | Total
Employee benefit plans
Fair value of plan assets		11.1
Government securities and corporate bond mutual funds | Total
Employee benefit plans
Fair value of plan assets	49.6	13.3
Funds-of-funds | Total
Employee benefit plans
Fair value of plan assets	45.9	61.3
Insurance Annuities | Total
Employee benefit plans
Fair value of plan assets	11.3	15.6
Cash and cash equivalents | Total
Employee benefit plans
Fair value of plan assets	14.6	0.7
Total Investments | Total
Employee benefit plans
Fair value of plan assets	121.4	142.3
Total pension plan assets | Total
Employee benefit plans
Fair value of plan assets	126.2	158.4
Quoted prices in active markets (Level 1) | U.S. mutual funds
Employee benefit plans
Fair value of plan assets		40.3
Quoted prices in active markets (Level 1) | International mutual funds
Employee benefit plans
Fair value of plan assets		11.1
Quoted prices in active markets (Level 1) | Cash and cash equivalents
Employee benefit plans
Fair value of plan assets	14.6	0.7
Quoted prices in active markets (Level 1) | Total Investments
Employee benefit plans
Fair value of plan assets	14.6	52.1
Significant other observable inputs (Level 2) | Government securities and corporate bond mutual funds
Employee benefit plans
Fair value of plan assets	49.6	13.3
Significant other observable inputs (Level 2) | Funds-of-funds
Employee benefit plans
Fair value of plan assets	45.9	61.3
Significant other observable inputs (Level 2) | Total Investments
Employee benefit plans
Fair value of plan assets	95.5	74.6
Significant other unobservable inputs (Level 3) | Insurance Annuities
Employee benefit plans
Fair value of plan assets	11.3	15.6	$ 11.7
Significant other unobservable inputs (Level 3) | Total Investments
Employee benefit plans
Fair value of plan assets	11.3	15.6
Measured at net asset value | Other investments measured at net asset value | Total
Employee benefit plans
Fair value of plan assets	$ 4.8	$ 16.1