Acquisitions (First Quarter 2014) - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016 Employee
Centric Insurance Agency [Member]
Business Acquisition, Contingent Consideration [Line Items]
Acquired entity, name	Centric Insurance Agency
Effective date of acquisition	Jan. 01, 2014
Clearview National Partners, L.L.C [Member]
Business Acquisition, Contingent Consideration [Line Items]
Acquired entity, name	Clearview National Partners, LLC
Effective date of acquisition	Jan. 01, 2014
Clearview National Partners, L.L.C [Member] | Minimum [Member]
Business Acquisition, Contingent Consideration [Line Items]
Number of employees covered	100
Lewis Birch & Richardo, LLC [Member]
Business Acquisition, Contingent Consideration [Line Items]
Acquired entity, name	Lewis Birch & Richardo, LLC
Effective date of acquisition	Feb. 01, 2014