Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	$ 6,095,626	$ 6,022,473
Equity securities - available for sale, at fair value	426,089	517,466
Short-term investments*	427,700	178,753
Restricted cash and securities	2,022	1,853
Premium, claims and other receivables	71,463	66,515
Other assets	1,187	961
Total assets measured at fair value	7,024,087	6,788,021
Notes payable	773,615	707,656
Accounts payable and accrued liabilities - earnout liability	9,344	9,112
Total liabilities measured at fair value	782,959	716,768
Fair Value, Inputs, Level 1 [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	83,462	84,032
Equity securities - available for sale, at fair value	426,089	517,466
Short-term investments*	268,479	68,958
Other assets	20	20
Total assets measured at fair value	778,050	670,476
Fair Value, Inputs, Level 2 [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	6,012,014	5,929,024
Short-term investments*	159,221	109,795
Restricted cash and securities	2,022	1,853
Premium, claims and other receivables	71,463	66,515
Total assets measured at fair value	6,244,720	6,107,187
Notes payable	773,615	707,656
Accounts payable and accrued liabilities - earnout liability	2,022	1,853
Total liabilities measured at fair value	775,637	709,509
Fair Value, Inputs, Level 3 [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	150	9,417
Other assets	1,167	941
Total assets measured at fair value	1,317	10,358
Accounts payable and accrued liabilities - earnout liability	7,322	7,259
Total liabilities measured at fair value	7,322	7,259
US Government and Government Agency Securities [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	92,097	92,709
US Government and Government Agency Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	83,462	84,032
US Government and Government Agency Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	8,635	8,677
Fixed Maturity Securities of States, Municipalities and Political Subdivisions Securities [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	988,817	986,486
Fixed Maturity Securities of States, Municipalities and Political Subdivisions Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	988,817	986,486
Special Purpose Revenue Bonds Of States Municipalities And Political Subdivisions [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	2,321,316	2,265,195
Special Purpose Revenue Bonds Of States Municipalities And Political Subdivisions [Member] | Fair Value, Inputs, Level 2 [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	2,321,316	2,255,928
Special Purpose Revenue Bonds Of States Municipalities And Political Subdivisions [Member] | Fair Value, Inputs, Level 3 [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale		9,267
Corporate Securities [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	1,211,187	1,225,238
Corporate Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	1,211,037	1,225,088
Corporate Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	150	150
Residential Mortgage Backed Securities [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	637,289	618,119
Residential Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	637,289	618,119
Commercial Mortgage Backed Securities [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	516,532	504,888
Commercial Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	516,532	504,888
Asset-backed Securities [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	234,263	182,392
Asset-backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	234,263	182,392
Foreign Government Securities [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	94,125	147,446
Foreign Government Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	$ 94,125	$ 147,446