Investments (Schedule Of Amortized Cost, Unrealized Gains And Losses, And Market Value Of Investment Securities) (Details) (USD $)	Mar. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 201,719,645	$ 179,388,001
Unrealized Gains	32,916,158	23,937,617
Unrealized Losses	(472,407)	(688,728)
Investments	234,163,396	202,636,890
Short-Term Investments [Member] | Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	48,452,720	38,514,411
Unrealized Gains	11,129	9,004
Unrealized Losses	(2,736)	(944)
Investments	48,461,113	38,522,471
Short-Term Investments [Member] | U.S. Treasury Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	18,045,049	15,018,810
Unrealized Gains	5,655	2,602
Unrealized Losses	(274)	(1,062)
Investments	18,050,430	15,020,350
Short-Term Investments [Member] | Corporate Bond Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	8,466,427	6,529,758
Unrealized Gains	19,284	33,470
Unrealized Losses	(10,727)	0
Investments	8,474,984	6,563,228
Short-Term Investments [Member] | Other [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	454,583	185,926
Unrealized Gains	0	0
Unrealized Losses	0	0
Investments	454,583	185,926
Short-Term Investments [Member] | Certificate Of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	510,881	510,881
Unrealized Gains	0	0
Unrealized Losses	0	0
Investments	510,881	510,881
Long-Term Investments [Member] | U.S. Treasury Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	5,151,204
Unrealized Gains	0
Unrealized Losses	(404)
Investments	5,150,800
Long-Term Investments [Member] | Corporate Bond Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	2,144,434	2,174,948
Unrealized Gains	7,106	5,832
Unrealized Losses	0	0
Investments	2,151,540	2,180,780
Long-Term Investments [Member] | Common Stocks [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	39,517,584	40,893,121
Unrealized Gains	14,913,846	12,781,501
Unrealized Losses	(392,435)	(391,421)
Investments	54,038,995	53,283,201
Long-Term Investments [Member] | Mutual Funds - Equity [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	78,976,763	75,321,640
Unrealized Gains	17,959,138	11,082,714
Unrealized Losses	(65,831)	(295,301)
Investments	96,870,070	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