Annual report pursuant to Section 13 and 15(d)

Description of Business, Basis of Presentation, and Significant Accounting Policies (Narrative) (Details)

v3.22.2
Description of Business, Basis of Presentation, and Significant Accounting Policies (Narrative) (Details)
 12 Months Ended
May 31, 2022
USD ($)
Item
Segment
May 31, 2021
USD ($)
Item
May 31, 2020
USD ($)
Item
Accounting Policies [Line Items]      
Number of reportable segments | Segment 1    
Cash and cash equivalents $ 370,000,000.0 $ 995,200,000 $ 905,200,000
Allowance for credit losses 18,200,000 16,000,000.0  
Advance collections 2,600,000 2,500,000  
Goodwill 1,831,500,000 1,820,700,000 1,791,100,000
Goodwill, impairment loss 0 0 0
Impairment of intangible assets with indefinite useful lives 0 0 0
Impairment of long-lived assets 0 0 0
Realized gains or losses from foreign exchange transactions 0 0 0
Impairment loss, assets recognized from the costs to obtain and fufill contracts 0 0 0
Workers' compensation insurance costs in current liabilities 64,100,000 65,300,000  
Workers' compensation insurance costs in long-term liabilities 125,600,000 117,800,000  
Maximum individual health insurance claims liability 500,000 300,000  
PEO accrued health insurance and dental and vision plan reserves in current liabilities 46,200,000 43,900,000  
Operating lease, impairment loss $ 0 0 $ 0
Accounting Standards Update 2020-08 [Member]      
Accounting Policies [Line Items]      
Change in accounting principle, accounting standards update, adoption date Jun. 30, 2021    
Change in accounting principle, accounting standards update, adopted [true false] true    
Change in accounting principle, accounting standards update, immaterial effect [true false] true    
Accounting Standards Update 2019-12 [Member]      
Accounting Policies [Line Items]      
Change in accounting principle, accounting standards update, adoption date Jun. 30, 2021    
Change in accounting principle, accounting standards update, adopted [true false] true    
Change in accounting principle, accounting standards update, immaterial effect [true false] true    
Trade Receivables [Member]      
Accounting Policies [Line Items]      
Receivables $ 123,200,000 98,400,000  
Purchased Receivables [Member]      
Accounting Policies [Line Items]      
Receivables $ 618,800,000 $ 495,900,000  
Minimum [Member]      
Accounting Policies [Line Items]      
Payroll funding fees average collection period 46 days    
Minimum [Member] | Finite Lived Assets [Member]      
Accounting Policies [Line Items]      
Amortization period 3 years    
Minimum [Member] | Software [Member]      
Accounting Policies [Line Items]      
Estimated useful lives 3 years    
Minimum [Member] | Software Development [Member]      
Accounting Policies [Line Items]      
Estimated useful lives 12 years    
Maximum [Member]      
Accounting Policies [Line Items]      
Payroll funding fees average collection period 48 days    
Maximum [Member] | Finite Lived Assets [Member]      
Accounting Policies [Line Items]      
Amortization period 12 years    
Maximum [Member] | Software [Member]      
Accounting Policies [Line Items]      
Estimated useful lives 5 years    
Revenue [Member]      
Accounting Policies [Line Items]      
Number of clients creating a credit concentration | Item 0 0 0
Accounts And Unbilled Receivables [Member]      
Accounting Policies [Line Items]      
Number of clients creating a credit concentration | Item 0 0  
INDIA [Member] | Long Lived Assets [Member] | Geographic Concentration Risk [Member] | Maximum [Member]      
Accounting Policies [Line Items]      
Concentration percentage 1.00% 1.00%  
Europe [Member] | Revenue [Member] | Geographic Concentration Risk [Member]      
Accounting Policies [Line Items]      
Concentration percentage 1.00% 1.00% 1.00%
Europe [Member] | Long Lived Assets [Member] | Geographic Concentration Risk [Member]      
Accounting Policies [Line Items]      
Concentration percentage 6.00% 7.00%  
PEO Aggregate Claims Exceeding $1.0M [Member] | Minimum [Member]      
Accounting Policies [Line Items]      
Individual Claims Liability Workers Compensation Insurance $ 1,000,000.0    
PEO Aggregate Claims Exceeding $1.0M [Member] | Maximum [Member]      
Accounting Policies [Line Items]      
Maximum individual workers' compensation claims liability 2,000,000.0    
PEO And Insurance Solutions [Member]      
Accounting Policies [Line Items]      
Cash and cash equivalents 89,700,000 $ 150,500,000  
PEO [Member]      
Accounting Policies [Line Items]      
Maximum individual workers' compensation claims liability   $ 1,000,000.0  
Individual Claims Liability Workers Compensation Insurance $ 1,000,000.0