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
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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.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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-Paragraph 2
-Subparagraph (c)
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
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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
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-URI http://asc.fasb.org/extlink&oid=6506951

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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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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-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
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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 Trading Securities
-URI http://asc.fasb.org/extlink&oid=6526789

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
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Reference 5: http://www.xbrl.org/2003/role/presentationRef
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-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 1
-Subparagraph a, f, g
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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Investments (Schedule of Amortized Cost, Unrealized Gains And Losses, And Market Value of Investment Securities) (Details) - USD ($)	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Cash & Cash Equivalents	$ 626,470,720	$ 551,557,527
Cost	79,701,563	98,427,114
Unrealized Gains	5,019,908	6,146,311
Unrealized Losses	(4,062,477)	(4,869,531)
Market Value	80,658,994	99,703,894
Investments and Cash	707,129,714	651,261,421
Short-term Investments [Member] \| US Government Agencies Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	3,008,955	3,013,482
Unrealized Gains	1,725	0
Unrealized Losses	0	(2,622)
Market Value	3,010,680	3,010,860	$ 3,010,680
Short-term Investments [Member] \| Corporate Bond Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	1,501,654	1,512,405
Unrealized Gains	0	0
Unrealized Losses	(319)	(390)
Market Value	1,501,335	1,512,015	1,501,335
Short-term Investments [Member] \| Other Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	30,049	24,480
Unrealized Gains	0	0
Unrealized Losses	0	0
Market Value	30,049	24,480
Short-term Investments [Member] \| Mutual Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	4,997,416
Unrealized Gains	55,782
Unrealized Losses	0
Market Value	5,053,198		5,053,198
Long-Term Investments [Member] \| Common Stocks [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	14,168,958	17,395,641
Unrealized Gains	3,716,147	4,078,912
Unrealized Losses	(815,854)	(1,019,749)
Market Value	17,069,251	20,454,804
Long-Term Investments [Member] \| Mutual Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	55,994,531	76,481,106
Unrealized Gains	1,246,254	2,067,399
Unrealized Losses	(3,246,304)	(3,846,770)
Market Value	53,994,481	74,701,735
Long-Term Investments [Member] \| Other Equity [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	0
Unrealized Gains	0
Unrealized Losses	0
Market Value	0
Fair Value, Inputs, Level 1 [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash & Cash Equivalents	626,470,720	551,557,527
Investments and Cash	697,564,501	646,738,546
Fair Value, Inputs, Level 1 [Member] \| Short-term Investments [Member] \| US Government Agencies Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Market Value		0	0
Fair Value, Inputs, Level 1 [Member] \| Short-term Investments [Member] \| Corporate Bond Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Market Value		0	0
Fair Value, Inputs, Level 1 [Member] \| Short-term Investments [Member] \| Other Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Market Value	30,049	24,480
Fair Value, Inputs, Level 1 [Member] \| Short-term Investments [Member] \| Mutual Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Market Value			0
Fair Value, Inputs, Level 1 [Member] \| Long-Term Investments [Member] \| Common Stocks [Member]
Schedule of Available-for-sale Securities [Line Items]
Market Value	17,069,251	20,454,804
Fair Value, Inputs, Level 1 [Member] \| Long-Term Investments [Member] \| Mutual Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Market Value	53,994,481	74,701,735
Fair Value, Inputs, Level 2 [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash & Cash Equivalents	0	0
Investments and Cash	9,565,213	4,522,875
Fair Value, Inputs, Level 2 [Member] \| Short-term Investments [Member] \| US Government Agencies Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Market Value		3,010,860	3,010,680
Fair Value, Inputs, Level 2 [Member] \| Short-term Investments [Member] \| Corporate Bond Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Market Value		1,512,015	1,501,335
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] \| Short-term Investments [Member] \| Mutual Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Market Value			5,053,198
Fair Value, Inputs, Level 2 [Member] \| Long-Term Investments [Member] \| Common Stocks [Member]
Schedule of Available-for-sale Securities [Line Items]
Market Value	0	0
Fair Value, Inputs, Level 2 [Member] \| Long-Term Investments [Member] \| Mutual Funds [Member]
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] \| US Government Agencies Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Market Value		0	0
Fair Value, Inputs, Level 3 [Member] \| Short-term Investments [Member] \| Corporate Bond Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Market Value		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] \| Short-term Investments [Member] \| Mutual Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Market Value			$ 0
Fair Value, Inputs, Level 3 [Member] \| Long-Term Investments [Member] \| Common Stocks [Member]
Schedule of Available-for-sale Securities [Line Items]
Market Value	0	0
Fair Value, Inputs, Level 3 [Member] \| Long-Term Investments [Member] \| Mutual Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Market Value	$ 0	$ 0