Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	$ 6,194,625	$ 6,281,781
Equity securities - available for sale, at fair value	433,345	284,639
Short-term investments*	229,191	363,053
Other Investments	0	20,925
Restricted cash and securities	1,846	2,043
Premium, claims and other receivables	65,490	68,207
Other assets	848	349
Total assets measured at fair value	6,925,345	7,020,997
Notes payable	701,881	636,363
Accounts payable and accrued liabilities - earnout liability	9,041	9,052
Accounts payable and accrued liabilities - forward contract		3,194
Total liabilities measured at fair value	710,922	648,609
Fair Value, Inputs, Level 1 [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	97,279	174,520
Equity securities - available for sale, at fair value	433,345	284,639
Short-term investments*	107,350	251,988
Other Investments Held At Fair Value	0	20,925
Other assets	17
Total assets measured at fair value	637,991	732,072
Fair Value, Inputs, Level 2 [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	6,087,983	6,107,097
Short-term investments*	121,841	111,065
Restricted cash and securities	1,846	2,043
Premium, claims and other receivables	65,490	68,207
Total assets measured at fair value	6,277,160	6,288,412
Notes payable	701,881	636,363
Accounts payable and accrued liabilities - earnout liability	1,846	2,043
Accounts payable and accrued liabilities - forward contract		3,194
Total liabilities measured at fair value	703,727	641,600
Fair Value, Inputs, Level 3 [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	9,363	164
Other assets	831	349
Total assets measured at fair value	10,194	513
Accounts payable and accrued liabilities - earnout liability	7,195	7,009
Total liabilities measured at fair value	7,195	7,009
US Government and Government Agency Securities [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	117,505	199,607
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	97,279	174,520
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	20,226	25,087
Fixed Maturity Securities of States, Municipalities and Political Subdivisions Securities [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	1,016,139	1,065,811
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	1,016,139	1,065,811
Special Purpose Revenue Bonds Of States Municipalities And Political Subdivisions [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	2,296,838	2,200,331
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	2,287,625	2,200,331
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	9,213
Corporate Securities [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	1,297,704	1,315,170
Corporate Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	1,297,554	1,315,006
Corporate Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	150	164
Residential Mortgage Backed Securities [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	592,957	664,887
Residential Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	592,957	664,887
Commercial Mortgage Backed Securities [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	531,216	524,289
Commercial Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	531,216	524,289
Asset-backed Securities [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	141,301	33,275
Asset-backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	141,301	33,275
Foreign Government Securities [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	200,965	278,411
Foreign Government Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fixed maturity securities-available for sale
Fixed maturity securities - available for sale	$ 200,965	$ 278,411