Investments (Amortized Cost and Estimated Fair Value of Investments in Debt and Equity Securities by Category) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Schedule of Investments [Line Items]
Investments, Amortized Cost	$ 419,893	$ 429,302
Investments, Gross Unrealized Gains	27,460	20,887
Investments, Gross Unrealized Losses	(4,766)	(4,829)
Investments, Fair Value	442,587	445,360
Equity Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	24,033	31,502
Investments, Gross Unrealized Gains	22,629	12,938
Investments, Gross Unrealized Losses	(722)	(515)
Investments, Fair Value	45,940	43,925
Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	395,860	397,800
Investments, Gross Unrealized Gains	4,831	7,949
Investments, Gross Unrealized Losses	(4,044)	(4,314)
Investments, Fair Value	396,647	401,435
Us Treasury Securities and Obligations of U.S. Government [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	34,083	40,050
Investments, Gross Unrealized Gains	31	14
Investments, Gross Unrealized Losses		(3)
Investments, Fair Value	34,114	40,061
Corporate Bonds [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	58,633	79,516
Investments, Gross Unrealized Gains	1,285	2,794
Investments, Gross Unrealized Losses	(525)	(763)
Investments, Fair Value	59,393	81,547
Collateralized Corporate Bank Loans [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	119,626	106,093
Investments, Gross Unrealized Gains	475	1,021
Investments, Gross Unrealized Losses	(549)	(743)
Investments, Fair Value	119,552	106,371
Municipal Bonds [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	153,974	162,479
Investments, Gross Unrealized Gains	2,701	4,023
Investments, Gross Unrealized Losses	(2,179)	(2,770)
Investments, Fair Value	154,496	163,732
Mortgage Backed [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	29,544	9,662
Investments, Gross Unrealized Gains	339	97
Investments, Gross Unrealized Losses	(791)	(35)
Investments, Fair Value	29,092	9,724
Financial Services [Member] | Equity Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	4,705	11,008
Investments, Gross Unrealized Gains	2,985	3,880
Investments, Gross Unrealized Losses		(1)
Investments, Fair Value	7,690	14,887
All Other [Member] | Equity Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	19,328	20,494
Investments, Gross Unrealized Gains	19,644	9,058
Investments, Gross Unrealized Losses	(722)	(514)
Investments, Fair Value	$ 38,250	$ 29,038