Description of Business, Basis of Presentation, and Significant Accounting Policies (Narrative) (Details) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Nov. 30, 2024 USD ($) Item	Nov. 30, 2023 USD ($) Item	Nov. 30, 2024 USD ($) Item Segment	Nov. 30, 2023 USD ($) Item	May 31, 2025 USD ($)	May 31, 2024 USD ($) Item
Accounting Policies [Line Items]
Number of reportable segments | Segment			1
Allowance for credit losses	$ 25.1		$ 25.1			$ 21.3
Advance collections	1.3		1.3			0.7
Maximum individual health insurance claims liability						0.5
Stock-based compensation costs recognized	$ 16.4	$ 14.7	$ 32.9	$ 30.7
Change in accounting principle, accounting standards update, adopted [true false]	false		false
Forecast [Member]
Accounting Policies [Line Items]
Maximum individual health insurance claims liability					$ 0.5
Trade Receivables [Member]
Accounting Policies [Line Items]
Receivables	$ 144.7		$ 144.7			141.3
Purchased Receivables [Member]
Accounting Policies [Line Items]
Receivables	$ 1,100.0		$ 1,100.0			$ 939.6
Accounts And Unbilled Receivables [Member]
Accounting Policies [Line Items]
Number of clients creating a credit concentration | Item			0			0
Revenue [Member]
Accounting Policies [Line Items]
Number of clients creating a credit concentration | Item	0	0	0	0
PEO Aggregate Claims Exceeding $1.0M [Member] | Minimum [Member]
Accounting Policies [Line Items]
Individual workers' compensation claims liability						$ 1.0
PEO Aggregate Claims Exceeding $1.0M [Member] | Minimum [Member] | Forecast [Member]
Accounting Policies [Line Items]
Individual workers' compensation claims liability					1.0
PEO Aggregate Claims Exceeding $1.0M [Member] | Maximum [Member]
Accounting Policies [Line Items]
Maximum individual workers' compensation claims liability						$ 1.0
PEO Aggregate Claims Exceeding $1.0M [Member] | Maximum [Member] | Forecast [Member]
Accounting Policies [Line Items]
Maximum individual workers' compensation claims liability					$ 1.0