Investments (Amortized Cost and Estimated Fair Value of Investments in Debt and Equity Securities by Category) (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Schedule of Investments [Line Items]
Investments, Amortized Cost	$ 435,967	$ 433,529
Investments, Gross Unrealized Gains	34,218	31,696
Investments, Gross Unrealized Losses	(4,245)	(3,900)
Investments, Fair Value	465,940	461,325
Equity Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	24,967	24,902
Investments, Gross Unrealized Gains	29,714	26,642
Investments, Gross Unrealized Losses	(3)	(314)
Investments, Fair Value	54,678	51,230
Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	411,000	408,627
Investments, Gross Unrealized Gains	4,504	5,054
Investments, Gross Unrealized Losses	(4,242)	(3,586)
Investments, Fair Value	411,262	410,095
US Treasury Securities and Obligations of U.S. Government [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	75,390	78,894
Investments, Gross Unrealized Gains	44	24
Investments, Gross Unrealized Losses	(76)	(165)
Investments, Fair Value	75,358	78,753
Corporate Bonds [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	29,569	42,946
Investments, Gross Unrealized Gains	1,183	1,379
Investments, Gross Unrealized Losses		(450)
Investments, Fair Value	30,752	43,875
Collateralized Corporate Bank Loans [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	113,839	102,053
Investments, Gross Unrealized Gains	192	614
Investments, Gross Unrealized Losses	(1,831)	(489)
Investments, Fair Value	112,200	102,178
Municipal Bonds [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	141,140	156,950
Investments, Gross Unrealized Gains	2,514	2,577
Investments, Gross Unrealized Losses	(1,666)	(1,975)
Investments, Fair Value	141,988	157,552
Mortgage Backed [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	51,062	27,784
Investments, Gross Unrealized Gains	571	460
Investments, Gross Unrealized Losses	(669)	(507)
Investments, Fair Value	$ 50,964	$ 27,737