Acquisitions - Additional Information (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2017 USD ($) Client_List shares	Mar. 31, 2016 USD ($) Client_List shares
Business Acquisition, Contingent Consideration [Line Items]
Increase (Decrease) in fair value of contingent consideration	$ 0.6	$ (1.3)
Consideration paid in cash	$ 2.9	$ 2.0
Number of common stock issued | shares	47,000	32,000
Acquisition of Client Lists [Member]
Business Acquisition, Contingent Consideration [Line Items]
Number of client list purchased | Client_List	0
Consideration paid in cash		$ 0.2
Guaranteed future consideration		1.0
Contingent consideration		$ 0.7
Acquisition of Client Lists [Member] | Benefit and Insurance Services Practice Group [Member]
Business Acquisition, Contingent Consideration [Line Items]
Number of client list purchased | Client_List		2