Investment Securities Available for Sale (Components of Investment Securities Available for Sale) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 142,344	$ 162,168
Gross Unrealized Gains	18,716	19,885
Gross Unrealized Losses	(206)	(77)
Fair Value	160,854	181,976
Marketable equity securities
Schedule of Available-for-sale Securities [Line Items]
Cost	38,172	47,502
Gross Unrealized Gains	17,343	19,833
Gross Unrealized Losses	(206)	(62)
Fair Value	55,309	67,273
Mutual funds invested in fixed income securities
Schedule of Available-for-sale Securities [Line Items]
Cost	20,307	20,126
Gross Unrealized Gains	211	0
Gross Unrealized Losses	0	(15)
Fair Value	20,518	20,111
Total marketable debt securities by maturity dates
Schedule of Available-for-sale Securities [Line Items]
Cost	83,865	94,540
Gross Unrealized Gains	1,162	52
Gross Unrealized Losses	0	0
Fair Value	$ 85,027	$ 94,592

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=65884222&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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-Section 50
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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-Section 45
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Amount before tax of unrealized gain 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
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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
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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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