Investments (Schedule of Amortized Cost, Unrealized Gains And Losses, And Market Value of Investment Securities) (Details) (USD $)	Jun. 30, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 200,724,769	$ 179,388,001
Unrealized Gains	29,020,385	23,937,617
Unrealized Losses	(250,974)	(688,728)
Investments	229,494,180	202,636,890
Short-Term Investments [Member] | Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	53,065,141	38,514,411
Unrealized Gains	6,139	9,004
Unrealized Losses	(8,921)	(944)
Investments	53,062,359	38,522,471
Short-Term Investments [Member] | U.S. Treasury Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	28,274,980	15,018,810
Unrealized Gains	5,971	2,602
Unrealized Losses	(1,711)	(1,062)
Investments	28,279,240	15,020,350
Short-Term Investments [Member] | Corporate Bond Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	10,484,488	6,529,758
Unrealized Gains	10,351	33,470
Unrealized Losses	(1,480)	0
Investments	10,493,359	6,563,228
Short-Term Investments [Member] | Other [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	420,413	185,926
Unrealized Gains		0
Unrealized Losses		0
Investments	420,413	185,926
Short-Term Investments [Member] | Certificate Of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	260,881	510,881
Unrealized Gains	0	0
Unrealized Losses	0	0
Investments	260,881	510,881
Long-Term Investments [Member] | U.S. Treasury Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	0
Unrealized Gains	0
Unrealized Losses	0
Investments	0
Long-Term Investments [Member] | Corporate Bond Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	0	2,174,948
Unrealized Gains	0	5,832
Unrealized Losses	0	0
Investments	0	2,180,780
Long-Term Investments [Member] | Common Stocks [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	34,990,852	40,893,121
Unrealized Gains	11,684,312	12,781,501
Unrealized Losses	(199,744)	(391,421)
Investments	46,475,420	53,283,201
Long-Term Investments [Member] | Mutual Funds - Equity [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	73,228,014	75,321,640
Unrealized Gains	17,313,612	11,082,714
Unrealized Losses	(39,118)	(295,301)
Investments	90,502,508	86,109,053
Long-Term Investments [Member] | Other - Equity [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost		238,506
Unrealized Gains		22,494
Unrealized Losses		0
Investments		$ 261,000