Acquisitions - Additional Information (Detail) (USD $)	9 Months Ended
	Sep. 30, 2013 Client_List	Sep. 30, 2012 Client_List Business
Business Acquisition, Contingent Consideration [Line Items]
Consideration paid in cash	$ 3,700,000	$ 12,300,000
Consideration paid in cash	400,000	1,700,000
CBIZ contingent consideration	4,600,000	6,800,000
Number of client list purchased	1	2
Fair value of contingent consideration	1,100,000	400,000
Number of business acquired		4
Consideration paid in common stock		1,700,000
Associated Insurance Agents [Member]
Business Acquisition, Contingent Consideration [Line Items]
Consideration paid in cash	4,100,000
Contingent arrangements arising from acquisitions	5,200,000
Fair value of contingent consideration	4,600,000
Goodwill	7,915,000
Number of common stock issued	201,000
Meridian Insurance Group, LLC (Meridian), Primarily Care, Inc. (PCI) Stoltz and Company, LTD., L.L.P (Stoltz), Trinity Risk Advisors, Inc.(Trinity), Strategic Employee Benefit Services-The Pruett Group, Inc. (SEBS-Pruett), ProMedical, Inc. (ProMedical), the employee benefit division of Leavitt Pacific Insurance Brokers, Inc. (Leavitt), Diversified Industries, Inc. d/b/a Payroll Control Systems (PCS) and PHBV Partners, L.L.P. (PHBV) [Member]
Business Acquisition, Contingent Consideration [Line Items]
Consideration paid in cash		18,800,000
Number of common stock issued		315,000
Common stock issued		251,100
Client lists [Member]
Business Acquisition, Contingent Consideration [Line Items]
Consideration paid in cash	300,000	400,000
CBIZ contingent consideration	$ 200,000	$ 2,500,000