Schedule IV - Reinsurance (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Direct Amount									$ 2,330,267	$ 2,183,258	$ 2,048,530
Assumed From Other Companies									23,209	34,653	44,464
Ceded to Other Companies									363,567	365,302	356,922
Total Net Premiums Earned	$ 516,087	$ 507,390	$ 490,309	$ 476,123	$ 469,850	$ 462,639	$ 463,625	$ 456,495	$ 1,989,909	$ 1,852,609	$ 1,736,072
Percentage of Amount Assumed to Net									1.00%	2.00%	3.00%
Accident and Health Insurance Segment [Member]
Direct Amount									$ 37	$ 44	$ 55
Assumed From Other Companies									0	0	0
Ceded to Other Companies									37	44	55
Total Net Premiums Earned									$ 0	$ 0	$ 0
Percentage of Amount Assumed to Net									0.00%	0.00%	0.00%
Property and liability insurance [Member]
Direct Amount									$ 2,330,230	$ 2,183,214	$ 2,048,475
Assumed From Other Companies									23,209	34,653	44,464
Ceded to Other Companies									363,530	365,258	356,867
Total Net Premiums Earned									$ 1,989,909	$ 1,852,609	$ 1,736,072
Percentage of Amount Assumed to Net									1.00%	2.00%	3.00%