Investments (Amortized Cost and Estimated Fair Value of Investments in Debt and Equity Securities by Category) (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2015	Dec. 31, 2014
Schedule of Investments [Line Items]
Investments, Amortized Cost	$ 522,331	$ 476,130
Investments, Gross Unrealized Gains	35,479	35,076
Investments, Gross Unrealized Losses	(7,127)	(3,977)
Investments, Fair Value	550,683	507,229
Equity Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	25,080	25,360
Investments, Gross Unrealized Gains	31,838	31,086
Investments, Gross Unrealized Losses	(289)	(2)
Investments, Fair Value	56,629	56,444
Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	497,251	450,770
Investments, Gross Unrealized Gains	3,641	3,990
Investments, Gross Unrealized Losses	(6,838)	(3,975)
Investments, Fair Value	494,054	450,785
US Treasury Securities and Obligations of U.S. Government [Member] \| Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	92,299	93,280
Investments, Gross Unrealized Gains	333	29
Investments, Gross Unrealized Losses	(5)	(4)
Investments, Fair Value	92,627	93,305
Corporate Bonds [Member] \| Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	30,655	28,643
Investments, Gross Unrealized Gains	696	884
Investments, Gross Unrealized Losses	(259)	(85)
Investments, Fair Value	31,092	29,442
Collateralized Corporate Bank Loans [Member] \| Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	117,279	115,358
Investments, Gross Unrealized Gains	394	206
Investments, Gross Unrealized Losses	(810)	(1,915)
Investments, Fair Value	116,863	113,649
Municipal Bonds [Member] \| Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	190,604	161,546
Investments, Gross Unrealized Gains	1,991	2,384
Investments, Gross Unrealized Losses	(5,085)	(1,601)
Investments, Fair Value	187,510	162,329
Mortgage Backed [Member] \| Debt Securities [Member]
Schedule of Investments [Line Items]
Investments, Amortized Cost	66,414	51,943
Investments, Gross Unrealized Gains	227	487
Investments, Gross Unrealized Losses	(679)	(370)
Investments, Fair Value	$ 65,962	$ 52,060

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.

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)

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Amount of unrealized gain before deducting unrealized loss on investments in debt and equity securities classified as available-for-sale securities.

+ 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 (b)

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Amount of unrealized loss before deducting unrealized gain on investments in available-for-sale securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

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-Section 50

-Paragraph 2

-Subparagraph (c)

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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

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