Investments (Amortized Cost and Estimated Fair Value of Investments in Debt and Equity Securities by Category) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Schedule of Investments [Line Items]
Investments, Amortized Cost	$ 597,540	$ 563,580
Investments, Gross Unrealized Gains	26,882	26,122
Investments, Gross Unrealized Losses	(10,336)	(10,873)
Investments, Fair Value	614,086	578,829
Equity Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	27,460	24,951
Investments, Gross Unrealized Gains	22,998	23,391
Investments, Gross Unrealized Losses	(1,130)	(838)
Investments, Fair Value	49,328	47,504
Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	570,080	538,629
Investments, Gross Unrealized Gains	3,884	2,731
Investments, Gross Unrealized Losses	(9,206)	(10,035)
Investments, Fair Value	564,758	531,325
Us Treasury Securities and Obligations of U.S. Government [Member] \| Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	74,338	76,323
Investments, Gross Unrealized Gains	231	7
Investments, Gross Unrealized Losses		(61)
Investments, Fair Value	74,569	76,269
Corporate Bonds [Member] \| Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	161,211	122,894
Investments, Gross Unrealized Gains	956	637
Investments, Gross Unrealized Losses	(1,472)	(1,822)
Investments, Fair Value	160,695	121,709
Collateralized Corporate Bank Loans [Member] \| Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	81,062	83,434
Investments, Gross Unrealized Gains	116	44
Investments, Gross Unrealized Losses	(787)	(1,882)
Investments, Fair Value	80,391	81,596
Municipal Bonds [Member] \| Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	196,870	196,446
Investments, Gross Unrealized Gains	2,194	1,888
Investments, Gross Unrealized Losses	(6,384)	(5,966)
Investments, Fair Value	192,680	192,368
Mortgage Backed [Member] \| Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	56,599	59,532
Investments, Gross Unrealized Gains	387	155
Investments, Gross Unrealized Losses	(563)	(304)
Investments, Fair Value	$ 56,423	$ 59,383

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

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- Definition

Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.2)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Sum of the carrying amounts as of the balance sheet date of all investments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1(h))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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