Quarterly report pursuant to Section 13 or 15(d)

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

v3.10.0.1
Description of Business, Basis of Presentation, and Significant Accounting Policies (Narrative) (Details)
$ in Millions
3 Months Ended 12 Months Ended
Aug. 31, 2018
USD ($)
segment
Aug. 31, 2017
USD ($)
Jun. 30, 2019
USD ($)
May 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Sep. 30, 2018
USD ($)
Jun. 30, 2018
USD ($)
May 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Sep. 30, 2017
USD ($)
Jun. 01, 2016
USD ($)
Accounting Policies [Line Items]                      
Number of reportable segments | segment 1                    
Stock-based compensation costs recognized $ 10.9 $ 8.7                  
Maximum individual workers' compensation claims liability       $ 1.0       $ 1.3      
Maximum individual health insurance claims liability         $ 0.3       $ 0.3    
ASU 2014-09 [Member]                      
Accounting Policies [Line Items]                      
Cumulative adjustment to increase stockholder's equity                     $ 262.9
HR Outsourcing Holdings, Inc. [Member]                      
Accounting Policies [Line Items]                      
Maximum individual workers' compensation claims liability           $ 0.5       $ 0.5  
Maximum individual health insurance claims liability             $ 0.3        
HR Outsourcing Holdings, Inc. [Member] | Scenario, Forecast [Member]                      
Accounting Policies [Line Items]                      
Maximum individual health insurance claims liability     $ 0.3                
Europe [Member] | Revenue [Member] | Geographic Concentration Risk [Member]                      
Accounting Policies [Line Items]                      
Total percentage 1.00%                    
Europe [Member] | Revenue [Member] | Geographic Concentration Risk [Member] | Maximum [Member]                      
Accounting Policies [Line Items]                      
Total percentage   1.00%                  
Europe [Member] | Long Lived Assets [Member] | Geographic Concentration Risk [Member]                      
Accounting Policies [Line Items]                      
Total percentage 10.00%             10.00%