Reportable Segments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Reportable Segments [Abstract]
Number of reportable segments									2
Segment Reporting Information [Line Items]
Direct and assumed premium written									$ 341,286	$ 334,526	$ 295,802
Net premiums earned	61,402	54,853	59,655	61,551	64,196	60,429	62,344	57,601	237,461	244,570	214,738
Underwriting gain (loss)									44,058	(25,467)	19,583
Reconciliation from Segment Totals to Consolidated [Abstract]
Underwriting gain (loss)									44,058	(25,467)	19,583
Net investment income									9,930	10,729	11,335
Net realized gains (losses) on investments									9,011	(17,803)	16,485
Corporate expenses									(16,393)	(12,748)	(12,590)
Income (loss) before federal income taxes									46,606	(45,289)	34,813
Revenue, Major Customer [Line Items]
Direct And Assumed Premiums Written									341,286	334,526	295,802
Property and Casualty Insurance [Member] | FedEx Ground, Certain Subsidiaries, and Related Entities [Member]
Segment Reporting Information [Line Items]
Direct and assumed premium written									19,052	23,347	20,187
Revenue, Major Customer [Line Items]
Number of major customer									1
Direct And Assumed Premiums Written									19,052	23,347	20,187
Property and Casualty Insurance [Member] | Non-affiliated Broker on Behalf of Independent Contractors [Member]
Segment Reporting Information [Line Items]
Direct and assumed premium written									146,447	129,508	115,625
Revenue, Major Customer [Line Items]
Direct And Assumed Premiums Written									146,447	129,508	115,625
Property and Casualty Insurance [Member]
Segment Reporting Information [Line Items]
Direct and assumed premium written									284,200	274,101	249,699
Net premiums earned									186,586	186,422	174,043
Underwriting gain (loss)									23,491	19,646	26,308
Reconciliation from Segment Totals to Consolidated [Abstract]
Underwriting gain (loss)									23,491	19,646	26,308
Revenue, Major Customer [Line Items]
Direct And Assumed Premiums Written									284,200	274,101	249,699
Reinsurance [Member]
Segment Reporting Information [Line Items]
Direct and assumed premium written									57,086	60,425	46,103
Net premiums earned									50,875	58,148	40,695
Underwriting gain (loss)									20,567	(45,113)	(6,725)
Reconciliation from Segment Totals to Consolidated [Abstract]
Underwriting gain (loss)									20,567	(45,113)	(6,725)
Revenue, Major Customer [Line Items]
Direct And Assumed Premiums Written									$ 57,086	$ 60,425	$ 46,103