Fair Value Measurements (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Investments, at Fair Value	$ 20,863	$ 35,754
Trading Securities	0	9,100
Total Assets	20,871	61,983
Securities Sold Short, at Fair Value	690	0
Total Liabilities	690
Money Market Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents	8	17,129
Equity Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Investments, at Fair Value	13,556	15,715
Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Investments, at Fair Value	7,307	20,039
U.S. Treasury Bills
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities	0	9,100
Fair Value | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets	20,416	52,363
Securities Sold Short, at Fair Value	690
Total Liabilities	690
Fair Value | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets	455	9,620
Fair Value | Money Market Funds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents	8	17,129
Fair Value | Equity Securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Investments, at Fair Value	13,101	15,195
Fair Value | Equity Securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Investments, at Fair Value	455	520
Fair Value | Mutual Funds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Investments, at Fair Value	$ 7,307	20,039
Fair Value | U.S. Treasury Bills | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities		$ 9,100