Acquisitions - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended			1 Months Ended			1 Months Ended	3 Months Ended	12 Months Ended
	Dec. 31, 2011 Agency Relationships Year	Dec. 31, 2011 Brokerage and Reinsurance Relationships Year	Dec. 31, 2011 Renewal and distribution rights Year	Dec. 31, 2006 Investment in Homesite	Dec. 29, 2006 Investment in Homesite	Jul. 18, 2008 ORX Exploration, Inc.	Jul. 31, 2007 Pacific Compensation Corporation	Jun. 30, 2009 Pacific Compensation Corporation	Dec. 31, 2008 Pacific Compensation Corporation	Jul. 18, 2007 Pacific Compensation Corporation
Business Acquisition [Line Items]
Purchase price to acquire business										$ 198.1
Acquisition costs incurred							5.6
Goodwill impairment charges									48.7
Impairment of intangible assets excluding goodwill								11.2
Other invested assets					120.0	50.0
Common stock acquired					85,714
Ownership Percentage					33.00%	38.00%
Transaction costs Incurred				$ 0.7
Economic useful life of intangible asset	15	15
Economic useful life of intangible asset, minimum			5
Economic useful life of intangible asset, maximum			10