Commitments and Contingencies - Legal Proceedings (Details) $ in Millions			3 Months Ended
	Dec. 19, 2016 USD ($)	Sep. 16, 2016 USD ($)	Mar. 31, 2021 USD ($) plaintiff
Baldino Group
Commitments And Contingencies [Line Items]
Number of plaintiffs | plaintiff			2
Damages sought amount			$ 16.0
Altoona Regional Health System | Minimum
Commitments And Contingencies [Line Items]
Damages sought amount		$ 124.0
Altoona Regional Health System | Maximum
Commitments And Contingencies [Line Items]
Damages sought amount		$ 266.0
CBIZ Operations and a former employee of CBIZ MMP
Commitments And Contingencies [Line Items]
Total transaction price	$ 200.0
CBIZ Operations and a former employee of CBIZ MMP | Maximum
Commitments And Contingencies [Line Items]
Damages sought amount	$ 177.0