Investments (Amortized Cost and Estimated Fair Value of Investments in Debt and Equity Securities) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Investments, Amortized Cost	$ 476,130	$ 433,529
Investments, Gross Unrealized Gains	35,076	31,696
Investments, Gross Unrealized Losses	(3,977)	(3,900)
Total investments	507,229us-gaap_Investments	461,325us-gaap_Investments
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Amortized Cost	25,360	24,902
Investments, Gross Unrealized Gains	31,086	26,642
Investments, Gross Unrealized Losses	(2)	(314)
Total investments	56,444	51,230
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Amortized Cost	450,770	408,627
Investments, Gross Unrealized Gains	3,990	5,054
Investments, Gross Unrealized Losses	(3,975)	(3,586)
Total investments	450,785	410,095
U.S. Treasury securities and obligations of U.S. Government [Member] \| Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Amortized Cost	93,280	78,894
Investments, Gross Unrealized Gains	29	24
Investments, Gross Unrealized Losses	(4)	(165)
Total investments	93,305	78,753
Corporate Bonds [Member] \| Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Amortized Cost	28,643	42,946
Investments, Gross Unrealized Gains	884	1,379
Investments, Gross Unrealized Losses	(85)	(450)
Total investments	29,442	43,875
Collateralized Corporate Bank Loans [Member] \| Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Amortized Cost	115,358	102,053
Investments, Gross Unrealized Gains	206	614
Investments, Gross Unrealized Losses	(1,915)	(489)
Total investments	113,649	102,178
Municipal Bonds [Member] \| Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Amortized Cost	161,546	156,950
Investments, Gross Unrealized Gains	2,384	2,577
Investments, Gross Unrealized Losses	(1,601)	(1,975)
Total investments	162,329	157,552
Collateralized Mortgage Backed Securities [Member] \| Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Amortized Cost	51,943	27,784
Investments, Gross Unrealized Gains	487	460
Investments, Gross Unrealized Losses	(370)	(507)
Total investments	$ 52,060	$ 27,737

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

-SubTopic 10

-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

-Subparagraph (SX 210.7-03.1(h))

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef

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