Loss and Loss Expense Reserves (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Activity in the reserve for losses and loss expenses [Roll Forward]
Reserves at the beginning of the year	$ 295,583	$ 288,088	$ 289,236
Provision for losses and loss expenses [Abstract]
Claims occurring during the current year	165,812	169,950	156,264
Claims occurring during prior years	(10,062)	(10,354)	(5,563)
Total incurred	155,750	159,596	150,701
Loss and loss expense payments [Abstract]
Claims occurring during the current year	56,710	59,826	47,908
Claims occurring during prior years	92,870	92,275	103,941
Total paid	149,580	152,101	151,849
Reserves at the end of the year	301,753	295,583	288,088
Reinsurance recoverable on unpaid losses at the end of the year	211,843	210,519	186,382
Reserves, gross of reinsurance recoverable, at the end of the year	513,596	506,102	474,470
Savings developed in settlements of claims with comparative developments for previous calendar years	$ 10,062
Period of comparative developments	2 years
Major Components of the Development of (Savings) deficiency [Abstract]
Property and casualty insurance	$ (10,289)	(5,423)	(1,725)
Reinsurance	227	(4,931)	(3,838)
Total	$ (10,062)	(10,354)	$ (5,563)
Workers' Compensation Discount [Abstract]
Loss reserves on certain permanent total disability workers' compensation reserves discounted to present value at pre-tax rates	3.50%
Amount of reduction in loss reserves	$ 2,110	$ 3,129