Acquisitions (Change in contingent purchase price liability related to prior acquisitions) - Additional Information (Detail) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2015	Sep. 30, 2014
Business Combinations [Abstract]
Fair value of contingent consideration	$ 3.1	$ 3.6

Business combination contingent consideration liability increase decrease adjustment.

No definition available.

Name:	cbz_BusinessCombinationContingentConsiderationLiabilityIncreaseDecreaseAdjustment
Namespace Prefix:	cbz_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration