Investments (Amortized Cost and Estimated Fair Value of Investments in Debt and Equity Securities by Category) (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2014	Dec. 31, 2013
Schedule of Investments [Line Items]
Investments, Amortized Cost	$ 449,590	$ 433,529
Investments, Gross Unrealized Gains	32,968	31,696
Investments, Gross Unrealized Losses	(2,858)	(3,900)
Investments, Fair Value	479,700	461,325
Equity Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	24,830	24,902
Investments, Gross Unrealized Gains	27,725	26,642
Investments, Gross Unrealized Losses	(2)	(314)
Investments, Fair Value	52,553	51,230
Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	424,760	408,627
Investments, Gross Unrealized Gains	5,243	5,054
Investments, Gross Unrealized Losses	(2,856)	(3,586)
Investments, Fair Value	427,147	410,095
US Treasury Securities and Obligations of U.S. Government [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	75,389	78,894
Investments, Gross Unrealized Gains	59	24
Investments, Gross Unrealized Losses	(3)	(165)
Investments, Fair Value	75,445	78,753
Corporate Bonds [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	35,874	42,946
Investments, Gross Unrealized Gains	1,384	1,379
Investments, Gross Unrealized Losses	(17)	(450)
Investments, Fair Value	37,241	43,875
Collateralized Corporate Bank Loans [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	105,096	102,053
Investments, Gross Unrealized Gains	468	614
Investments, Gross Unrealized Losses	(837)	(489)
Investments, Fair Value	104,727	102,178
Municipal Bonds [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	155,771	156,950
Investments, Gross Unrealized Gains	2,834	2,577
Investments, Gross Unrealized Losses	(1,291)	(1,975)
Investments, Fair Value	157,314	157,552
Mortgage Backed [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	52,630	27,784
Investments, Gross Unrealized Gains	498	460
Investments, Gross Unrealized Losses	(708)	(507)
Investments, Fair Value	$ 52,420	$ 27,737