Investments (Schedule of Amortized Cost, Unrealized Gains And Losses, And Market Value of Investment Securities) (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Cash & Cash Equivalents	$ 549,911,648	$ 497,429,804
Cost	99,354,849	97,923,092
Unrealized Gains	16,934,512	17,855,921
Unrealized Losses	(791,701)	(1,135,425)
Market Value	115,497,660us-gaap_InvestmentsFairValueDisclosure	114,643,588us-gaap_InvestmentsFairValueDisclosure
Investments and Cash	665,409,308us-gaap_InvestmentsAndCash	612,073,392us-gaap_InvestmentsAndCash
Short-term Investments [Member] \| Other Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	560	1,021
Unrealized Gains	0	0
Unrealized Losses	0	0
Market Value	560	1,021
Long-Term Investments [Member] \| Common Stock
Schedule of Available-for-sale Securities [Line Items]
Cost	18,804,767	17,069,742
Unrealized Gains	5,825,050	7,933,717
Unrealized Losses	(467,952)	(355,008)
Market Value	24,161,865	24,648,451
Long-Term Investments [Member] \| Mutual Funds – Equity
Schedule of Available-for-sale Securities [Line Items]
Cost	80,549,522	80,852,329
Unrealized Gains	11,109,462	9,922,204
Unrealized Losses	(323,749)	(780,417)
Market Value	91,335,235	89,994,116
Fair Value, Inputs, Level 1 [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash & Cash Equivalents	549,911,648	497,429,804
Investments and Cash	665,409,308	612,073,392
Fair Value, Inputs, Level 1 [Member] \| Short-term Investments [Member] \| Other Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Market Value	560	1,021
Fair Value, Inputs, Level 1 [Member] \| Long-Term Investments [Member] \| Common Stock
Schedule of Available-for-sale Securities [Line Items]
Market Value	24,161,865	24,648,451
Fair Value, Inputs, Level 1 [Member] \| Long-Term Investments [Member] \| Mutual Funds – Equity
Schedule of Available-for-sale Securities [Line Items]
Market Value	91,335,235	89,994,116
Fair Value, Inputs, Level 2 [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash & Cash Equivalents	0	0
Investments and Cash	0	0
Fair Value, Inputs, Level 2 [Member] \| Short-term Investments [Member] \| Other Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Market Value	0	0
Fair Value, Inputs, Level 2 [Member] \| Long-Term Investments [Member] \| Common Stock
Schedule of Available-for-sale Securities [Line Items]
Market Value	0	0
Fair Value, Inputs, Level 2 [Member] \| Long-Term Investments [Member] \| Mutual Funds – Equity
Schedule of Available-for-sale Securities [Line Items]
Market Value	0	0
Fair Value, Inputs, Level 3 [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash & Cash Equivalents	0	0
Investments and Cash	0	0
Fair Value, Inputs, Level 3 [Member] \| Short-term Investments [Member] \| Other Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Market Value	0	0
Fair Value, Inputs, Level 3 [Member] \| Long-Term Investments [Member] \| Common Stock
Schedule of Available-for-sale Securities [Line Items]
Market Value	0	0
Fair Value, Inputs, Level 3 [Member] \| Long-Term Investments [Member] \| Mutual Funds – Equity
Schedule of Available-for-sale Securities [Line Items]
Market Value	$ 0	$ 0

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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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

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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)

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Cash

-URI http://asc.fasb.org/extlink&oid=6506951

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-Name Accounting Standards Codification

-Glossary Cash Equivalents

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Sum of investments and unrestricted cash as of the balance sheet date.

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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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Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Available-for-Sale Securities

-URI http://asc.fasb.org/extlink&oid=6505594

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

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-Name Accounting Standards Codification

-Glossary Trading Securities

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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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-Name Regulation S-X (SX)

-Number 210

-Section 03

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-Subparagraph a, f, g

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