Acquisitions (Second quarter 2014) - Additional Information (Detail) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2014 USD ($) Business	Jun. 30, 2014 USD ($) Business	Mar. 31, 2014 USD ($) Business	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)
Business Acquisition, Contingent Consideration [Line Items]
Consideration paid in common stock				$ 2.0	$ 0.2
Contingent consideration				$ 4.2
Clearview National Partners, L.L.C, Centric Insurance Agency and Lewis Birch & Richardo, LLC [Member]
Business Acquisition, Contingent Consideration [Line Items]
Number of businesses acquired | Business	1	1	3
Consideration paid in cash	$ 3.1	$ 8.1	$ 16.5
Consideration paid in common stock		0.9	1.9
Contingent consideration	$ 1.9	$ 2.1	$ 10.2		$ 1.9