Investments (Investment Securities Stated At Fair Value) (Details) (USD $)	Mar. 31, 2012	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash & Cash Equivalents	$ 370,804,725	$ 357,986,774
Total	568,950,025	546,963,176
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash & Cash Equivalents	370,804,725	357,986,774
Total	535,026,277	520,764,582
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	33,923,748	26,198,594
Short-Term Investments [Member] | Government Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	21,006,150	35,024,030
Short-Term Investments [Member] | Government Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	21,006,150	35,024,030
Short-Term Investments [Member] | U.S. Treasury Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	25,022,500	25,044,000
Short-Term Investments [Member] | U.S. Treasury Notes [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	25,022,500	25,044,000
Short-Term Investments [Member] | Corporate Bond Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	5,730,158	649,204
Short-Term Investments [Member] | Corporate Bond Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	5,730,158	649,204
Short-Term Investments [Member] | Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	231,128	91,003
Short-Term Investments [Member] | Other Short-Term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	231,128	91,003
Short-Term Investments [Member] | Other Short-Term Investments [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	231,128	91,003
Long-Term Investments [Member] | Corporate Bond Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	2,665,700
Long-Term Investments [Member] | Corporate Bond Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	2,665,700
Long-Term Investments [Member] | Common Stocks [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	61,462,560	53,554,303
Long-Term Investments [Member] | Common Stocks [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	61,462,560	53,554,303
Long-Term Investments [Member] | Mutual Funds - Equity [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	81,167,814	73,749,772
Long-Term Investments [Member] | Mutual Funds - Equity [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	81,167,814	73,749,772
Long-Term Investments [Member] | Certificate Of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	505,390	505,390
Long-Term Investments [Member] | Certificate Of Deposit [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	505,390	505,390
Long-Term Investments [Member] | Other - Equity [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	353,900	358,700
Long-Term Investments [Member] | Other - Equity [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	$ 353,900	$ 358,700