Acquisitions (Second Quarter 2017) - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017
CMF Associates, LLC [Member]
Business Acquisition, Contingent Consideration [Line Items]
Effective date of acquisition	Jun. 01, 2017
Acquired entity, name	CMF Associates, LLC
Slaton Insurance [Member]
Business Acquisition, Contingent Consideration [Line Items]
Effective date of acquisition	Jun. 01, 2017
Acquired entity, name	Slaton Insurance