Investments (Amortized Cost and Estimated Fair Value of Investments in Debt and Equity Securities by Category) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Schedule of Investments [Line Items]
Investments, Amortized Cost	$ 412,407	$ 429,302
Investments, Gross Unrealized Gains	30,132	20,887
Investments, Gross Unrealized Losses	(5,299)	(4,829)
Investments, Fair Value	437,240	445,360
Equity Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	29,567	31,502
Investments, Gross Unrealized Gains	25,128	12,938
Investments, Gross Unrealized Losses	(1,137)	(515)
Investments, Fair Value	53,558	43,925
Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	382,840	397,800
Investments, Gross Unrealized Gains	5,004	7,949
Investments, Gross Unrealized Losses	(4,162)	(4,314)
Investments, Fair Value	383,682	401,435
Us Treasury Securities and Obligations of U.S. Government [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	37,623	40,050
Investments, Gross Unrealized Gains	8	14
Investments, Gross Unrealized Losses	(4)	(3)
Investments, Fair Value	37,627	40,061
Corporate Bonds [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	54,292	79,516
Investments, Gross Unrealized Gains	1,460	2,794
Investments, Gross Unrealized Losses	(703)	(763)
Investments, Fair Value	55,049	81,547
Collateralized Corporate Bank Loans [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	103,045	106,093
Investments, Gross Unrealized Gains	460	1,021
Investments, Gross Unrealized Losses	(457)	(743)
Investments, Fair Value	103,048	106,371
Municipal Bonds [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	155,927	162,479
Investments, Gross Unrealized Gains	2,826	4,023
Investments, Gross Unrealized Losses	(2,245)	(2,770)
Investments, Fair Value	156,508	163,732
Mortgage Backed [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	31,953	9,662
Investments, Gross Unrealized Gains	250	97
Investments, Gross Unrealized Losses	(753)	(35)
Investments, Fair Value	31,450	9,724
Financial Services [Member] | Equity Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	10,238	11,008
Investments, Gross Unrealized Gains	9,350	3,880
Investments, Gross Unrealized Losses		(1)
Investments, Fair Value	19,588	14,887
All Other [Member] | Equity Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	19,329	20,494
Investments, Gross Unrealized Gains	15,778	9,058
Investments, Gross Unrealized Losses	(1,137)	(514)
Investments, Fair Value	$ 33,970	$ 29,038