Investments (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Investments, Amortized Cost	$ 436,741	$ 429,302
Investments, Gross Unrealized Gains	28,362	20,887
Investments, Gross Unrealized Losses	(4,573)	(4,829)
Investments, Fair Value	460,530	445,360
Equity Securities [Member]
Investments, Amortized Cost	33,187	31,502
Investments, Gross Unrealized Gains	20,490	12,938
Investments, Gross Unrealized Losses	(888)	(515)
Investments, Fair Value	52,789	43,925
Debt Securities [Member]
Investments, Amortized Cost	403,554	397,800
Investments, Gross Unrealized Gains	7,872	7,949
Investments, Gross Unrealized Losses	(3,685)	(4,314)
Investments, Fair Value	407,741	401,435
US Treasury Securities and Obligation [Member] | Debt Securities [Member]
Investments, Amortized Cost	37,638	40,050
Investments, Gross Unrealized Gains	17	14
Investments, Gross Unrealized Losses	0	(3)
Investments, Fair Value	37,655	40,061
Corporate Bond Securities [Member] | Debt Securities [Member]
Investments, Amortized Cost	70,366	79,516
Investments, Gross Unrealized Gains	2,604	2,794
Investments, Gross Unrealized Losses	(909)	(763)
Investments, Fair Value	72,061	81,547
Collateralized Corporate Bank Loans [Member] | Debt Securities [Member]
Investments, Amortized Cost	100,511	106,093
Investments, Gross Unrealized Gains	1,163	1,021
Investments, Gross Unrealized Losses	(315)	(743)
Investments, Fair Value	101,359	106,371
Municipal Bonds [Member] | Debt Securities [Member]
Investments, Amortized Cost	161,183	162,479
Investments, Gross Unrealized Gains	3,860	4,023
Investments, Gross Unrealized Losses	(2,322)	(2,770)
Investments, Fair Value	162,721	163,732
Collateralized Mortgage Backed Securities [Member] | Debt Securities [Member]
Investments, Amortized Cost	33,856	9,662
Investments, Gross Unrealized Gains	228	97
Investments, Gross Unrealized Losses	(139)	(35)
Investments, Fair Value	33,945	9,724
Equity Securities Financial Services [Member] | Equity Securities [Member]
Investments, Amortized Cost	10,778	11,008
Investments, Gross Unrealized Gains	7,619	3,880
Investments, Gross Unrealized Losses	0	(1)
Investments, Fair Value	18,397	14,887
Equity Securities, Other [Member] | Equity Securities [Member]
Investments, Amortized Cost	22,409	20,494
Investments, Gross Unrealized Gains	12,871	9,058
Investments, Gross Unrealized Losses	(888)	(514)
Investments, Fair Value	$ 34,392	$ 29,038