Loss and Loss Expense Reserves (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Activity in the reserve for losses and loss expenses [Roll Forward]
Reserves at the beginning of the year	$ 289,236	$ 290,092	$ 218,629
Provision for losses and loss expenses:
Claims occurring during the current year	156,264	147,963	225,251
Claims occurring during prior years	(5,563)	(9,875)	(9,696)
Total incurred	150,701	138,088	215,555
Loss and loss expense payments:
Claims occurring during the current year	47,908	44,941	71,699
Claims occurring during prior years	103,941	94,003	72,393
Total paid	151,849	138,944	144,092
Reserves at the end of the year	288,088	289,236	290,092
Reinsurance recoverable on unpaid losses at the end of the year	186,382	166,218	131,464
Reserves, gross of reinsurance recoverable, at the end of the year	474,470	455,454	421,556
Savings developed in settlements of claims with comparative developments for previous calendar years	5,563
Period of comparative developments (in years)	2 years
Major Components of the Development of (Savings) deficiency [Abstract]
Property and casualty insurance	(1,725)	(7,111)	(7,417)
Reinsurance	(3,838)	(2,764)	(2,279)
Total	(5,563)	(9,875)	(9,696)
Workers' Compensation Discount [Abstract]
Loss reserves on certain permanent total disability workers' compensation reserves discounted to present value at pre-tax rates (in hundredths)	3.50%
Amount of reduction in loss reserves	5,885	6,118
Salvage and Subrogation Recoveries [Abstract]
Salvage and Subrogation Recoveries, Description	Loss reserves have been reduced by estimated salvage and subrogation recoverable.
Estimated salvage and subrogation recoverable	$ 8,115	$ 7,839