Business Combinations - Acquisition Method for Recording Business Combinations (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2013
Metzler Brothers Insurance [Member]
Business Acquisition [Line Items]
Effective Date of Acquisition	Feb. 01, 2013
Advanced Benefit Advisors, Inc.[Member]
Business Acquisition [Line Items]
Effective Date of Acquisition	Apr. 01, 2013
Property & Commercial Limited (PCL) [Member]
Business Acquisition [Line Items]
Effective Date of Acquisition	Apr. 01, 2013
Garza Long Group, LLC [Member]
Business Acquisition [Line Items]
Effective Date of Acquisition	May 01, 2013
Bollinger, Inc. (BOL) [Member]
Business Acquisition [Line Items]
Effective Date of Acquisition	Aug. 01, 2013
Dickinson & Associates, Inc. [Member]
Business Acquisition [Line Items]
Effective Date of Acquisition	Aug. 01, 2013
Belmont International (BEL) [Member]
Business Acquisition [Line Items]
Effective Date of Acquisition	Sep. 01, 2013
R.W. Scobie, Inc. [Member]
Business Acquisition [Line Items]
Effective Date of Acquisition	Sep. 01, 2013
Jeffrey Haber & Michael Fischman [Member]
Business Acquisition [Line Items]
Effective Date of Acquisition	Sep. 20, 2013
G.S. Levine Insurance Services, Inc. (GSL) [Member]
Business Acquisition [Line Items]
Effective Date of Acquisition	Oct. 01, 2013
R.J. Dutton Incorporated [Member]
Business Acquisition [Line Items]
Effective Date of Acquisition	Oct. 01, 2013
Employee Benefits Analysis Corporation [Member]
Business Acquisition [Line Items]
Effective Date of Acquisition	Nov. 01, 2013
Parks Johnson Agency, LLC [Member]
Business Acquisition [Line Items]
Effective Date of Acquisition	Nov. 01, 2013
Giles Group of Companies (GGC) [Member]
Business Acquisition [Line Items]
Effective Date of Acquisition	Nov. 14, 2013
Barmore Insurance Agency, Inc. [Member]
Business Acquisition [Line Items]
Effective Date of Acquisition	Dec. 01, 2013
Bergvall Marine A.S. (BMA) [Member]
Business Acquisition [Line Items]
Effective Date of Acquisition	Dec. 01, 2013
Cleaveland Insurance Group, Inc. [Member]
Business Acquisition [Line Items]
Effective Date of Acquisition	Dec. 01, 2013
The Jenkins Group, Inc. [Member]
Business Acquisition [Line Items]
Effective Date of Acquisition	Dec. 01, 2013
Longfellow Financial, LLC (LGF) [Member]
Business Acquisition [Line Items]
Effective Date of Acquisition	Dec. 01, 2013
McIntyre Risk Management, LLC (MRM) [Member]
Business Acquisition [Line Items]
Effective Date of Acquisition	Dec. 01, 2013