Employee Retirement Plans - Reconciliation of Changes in Projected Benefit Obligation and Fair Value of Plan Assets and Funded Status of Defined-benefit Plans (Detail) - USD ($) $ in Millions	12 Months Ended
	May 31, 2024	May 31, 2023	May 31, 2022
Change in benefit obligation
Interest cost	$ 3.6	$ 3.4	$ 1.4
Change in plan assets
Return on plan assets	4.0	3.9	2.1
Pension Benefit
Change in benefit obligation
Benefit obligation, beginning of year	76.9	82.3
Service cost	0.0	0.0
Interest cost	3.6	3.4
Plan amendments	0.0	0.0
Actuarial gain	(5.0)	(3.1)
Benefits paid	(5.4)	(5.7)
Benefit obligations acquired	1.0	0.0
Benefits obligation, end of year	71.1	76.9	82.3
Change in plan assets
Fair value, beginning of year	54.9	56.2
Return on plan assets	2.3	(0.5)
Company contributions	1.6	5.0
Benefits paid	(5.4)	(5.8)
Plan assets acquired	0.1	0.0
Fair value, end of year	53.5	54.9	56.2
Funded status	(17.6)	(22.0)
Amounts recognized in our consolidated and combined balance sheets consist of:
Amounts recognized in our consolidated balance sheets	(9.3)	(6.3)
Amounts recognized in AOCI consist of:
Net income	(9.3)	(6.3)
Net prior service credit	0.0	0.0
Total	(9.3)	(6.3)
Other Benefits
Change in benefit obligation
Benefit obligation, beginning of year	3.4	4.1
Service cost	0.0	0.0
Interest cost	0.2	0.2
Plan amendments	0.0	(0.4)
Actuarial gain	(0.2)	(0.3)
Benefits paid	(0.3)	(0.2)
Benefit obligations acquired	0.0	0.0
Benefits obligation, end of year	3.1	3.4	4.1
Change in plan assets
Fair value, beginning of year	0.0	0.0
Return on plan assets	0.0	0.0
Company contributions	0.3	0.2
Benefits paid	(0.3)	(0.2)
Plan assets acquired	0.0	0.0
Fair value, end of year	0.0	0.0	$ 0.0
Funded status	(3.1)	(3.4)
Amounts recognized in our consolidated and combined balance sheets consist of:
Amounts recognized in our consolidated balance sheets	(1.6)	(1.5)
Amounts recognized in AOCI consist of:
Net income	(1.2)	(1.1)
Net prior service credit	(0.4)	(0.4)
Total	(1.6)	(1.5)
Accrued Compensation, Contributions to Employee Benefit Plans and Related Taxes | Pension Benefit
Amounts recognized in our consolidated and combined balance sheets consist of:
Amounts recognized in our consolidated balance sheets	0.0	0.0
Amounts recognized in AOCI consist of:
Total	0.0	0.0
Accrued Compensation, Contributions to Employee Benefit Plans and Related Taxes | Other Benefits
Amounts recognized in our consolidated and combined balance sheets consist of:
Amounts recognized in our consolidated balance sheets	(0.3)	(0.3)
Amounts recognized in AOCI consist of:
Total	(0.3)	(0.3)
Other Liabilities | Pension Benefit
Amounts recognized in our consolidated and combined balance sheets consist of:
Amounts recognized in our consolidated balance sheets	(17.6)	(22.0)
Amounts recognized in AOCI consist of:
Total	(17.6)	(22.0)
Other Liabilities | Other Benefits
Amounts recognized in our consolidated and combined balance sheets consist of:
Amounts recognized in our consolidated balance sheets	(2.8)	(3.1)
Amounts recognized in AOCI consist of:
Total	(2.8)	(3.1)
AOCI | Pension Benefit
Amounts recognized in our consolidated and combined balance sheets consist of:
Amounts recognized in our consolidated balance sheets	(9.3)	(6.3)
Amounts recognized in AOCI consist of:
Total	(9.3)	(6.3)
AOCI | Other Benefits
Amounts recognized in our consolidated and combined balance sheets consist of:
Amounts recognized in our consolidated balance sheets	(1.6)	(1.5)
Amounts recognized in AOCI consist of:
Total	$ (1.6)	$ (1.5)