Investments (Amortized Cost and Estimated Fair Value of Investments in Debt and Equity Securities by Category) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Schedule of Investments [Line Items]
Investments, Amortized Cost	$ 642,969	$ 632,996
Investments, Gross Unrealized Gains	28,091	25,992
Investments, Gross Unrealized Losses	(2,061)	(4,869)
Investments, Fair Value	668,999	654,119
Other Investments [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	3,763	3,763
Investments, Gross Unrealized Gains	685	1,188
Investments, Fair Value	4,448	4,951
Equity Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	33,220	31,449
Investments, Gross Unrealized Gains	23,898	21,052
Investments, Gross Unrealized Losses	(641)	(790)
Investments, Fair Value	56,477	51,711
Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	605,986	597,784
Investments, Gross Unrealized Gains	3,508	3,752
Investments, Gross Unrealized Losses	(1,420)	(4,079)
Investments, Fair Value	608,074	597,457
Us Treasury Securities and Obligations of U.S. Government [Member] \| Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	42,014	41,976
Investments, Gross Unrealized Gains	11	66
Investments, Gross Unrealized Losses	(14)	(20)
Investments, Fair Value	42,011	42,022
Corporate Bonds [Member] \| Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	252,093	224,915
Investments, Gross Unrealized Gains	1,735	1,722
Investments, Gross Unrealized Losses	(161)	(575)
Investments, Fair Value	253,667	226,062
Collateralized Corporate Bank Loans [Member] \| Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	123,523	105,220
Investments, Gross Unrealized Gains	575	959
Investments, Gross Unrealized Losses	(292)	(170)
Investments, Fair Value	123,806	106,009
Municipal Bonds [Member] \| Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	153,475	165,900
Investments, Gross Unrealized Gains	1,043	956
Investments, Gross Unrealized Losses	(701)	(2,961)
Investments, Fair Value	153,817	163,895
Mortgage Backed [Member] \| Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	34,881	59,773
Investments, Gross Unrealized Gains	144	49
Investments, Gross Unrealized Losses	(252)	(353)
Investments, Fair Value	$ 34,773	$ 59,469

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=73527792&loc=d3e27161-111563

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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=73527792&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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