Acquisitions - Additional Information (Detail) (USD $)	3 Months Ended	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Business Acquisition, Contingent Consideration [Line Items]
Consideration paid in cash	$ 0	$ 1,500,000	$ 1,000,000
Goodwill	410,539,000	410,539,000		384,697,000
Fair value of contingent consideration	2,100,000	3,000,000	900,000
Number of common stock issued			136,000
Centric Insurance Agency (Centric), Clearview National Partners, LLC (Clearview) and Lewis Birch & Richardo, LLC (LBR) [Member]
Business Acquisition, Contingent Consideration [Line Items]
Number of businesses acquired		4
Consideration paid in cash		24,600,000
CBIZ contingent consideration	12,000,000	12,000,000
Consideration paid in common stock		2,900,000
Contingent arrangements arising from acquisitions	13,500,000	13,500,000
Contingent consideration	12,000,000	12,000,000
Goodwill	26,325,000	26,325,000
Associated Insurance Agents [Member]
Business Acquisition, Contingent Consideration [Line Items]
Consideration paid in cash			3,700,000
Contingent consideration			4,600,000
Guaranteed future consideration			400,000
Acquisition of Client Lists [Member]
Business Acquisition, Contingent Consideration [Line Items]
Consideration paid in cash			300,000
Contingent consideration			$ 200,000
Number of client list purchased			1