Schedule IV. Reinsurance (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross Amount	$ 5,300,305	$ 5,206,065	$ 4,916,833
Ceded to Other Companies	1,112,688	1,083,410	974,556
Assumed from Other Companies	4	22	42
Net Amount	4,187,621	4,122,677	3,942,319
Property and Casualty Insurance [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross Amount	726,221	659,989	564,506
Ceded to Other Companies	50,514	47,467	45,604
Assumed from Other Companies	18,485	16,889	14,869
Net Amount	694,192	629,411	533,771
Percentage of Amount Assumed to Net Earned	2.66%	2.68%	2.79%
Life Insurance [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross Amount	63,446	68,204	55,330
Ceded to Other Companies	2,792	2,621	2,318
Assumed from Other Companies	0	0	0
Net Amount	60,654	65,583	53,012
Percentage of Amount Assumed to Net Earned	0.00%	0.00%	0.00%
Total [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross Amount	789,667	728,193	619,836
Ceded to Other Companies	53,306	50,088	47,922
Assumed from Other Companies	18,485	16,889	14,869
Net Amount	$ 754,846	$ 694,994	$ 586,783
Percentage of Amount Assumed to Net Earned	2.45%	2.43%	2.53%