Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Investments in securities [Abstract]
Investments in securities	$ 15,071	$ 27,726
Common Stocks [Member]
Investments in securities [Abstract]
Investments in securities	13,645	26,463
Mutual Funds [Member]
Investments in securities [Abstract]
Investments in securities	960	752
Closed-end Funds [Member]
Investments in securities [Abstract]
Investments in securities	466	511
Recurring Basis [Member]
Assets [Abstract]
Cash equivalents	19,919	85,823
Investments in securities [Abstract]
Investments in securities	15,071	27,726
Total assets at fair value	34,990	113,549
Recurring Basis [Member] | Common Stocks [Member]
Investments in securities [Abstract]
Investments in securities	13,645	26,463
Recurring Basis [Member] | Mutual Funds [Member]
Investments in securities [Abstract]
Investments in securities	960	511
Recurring Basis [Member] | Closed-end Funds [Member]
Investments in securities [Abstract]
Investments in securities	466	752
Recurring Basis [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets [Abstract]
Cash equivalents	19,919	85,823
Investments in securities [Abstract]
Investments in securities	15,071	27,726
Total assets at fair value	34,990	113,549
Recurring Basis [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Common Stocks [Member]
Investments in securities [Abstract]
Investments in securities	13,645	26,463
Recurring Basis [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Mutual Funds [Member]
Investments in securities [Abstract]
Investments in securities	960	511
Recurring Basis [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Closed-end Funds [Member]
Investments in securities [Abstract]
Investments in securities	466	752
Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets [Abstract]
Cash equivalents	0	0
Investments in securities [Abstract]
Investments in securities	0	0
Total assets at fair value	0	0
Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | Common Stocks [Member]
Investments in securities [Abstract]
Investments in securities	0	0
Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | Mutual Funds [Member]
Investments in securities [Abstract]
Investments in securities	0	0
Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | Closed-end Funds [Member]
Investments in securities [Abstract]
Investments in securities	0	0
Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member]
Assets [Abstract]
Cash equivalents	0	0
Investments in securities [Abstract]
Investments in securities	0	0
Total assets at fair value	0	0
Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member] | Common Stocks [Member]
Investments in securities [Abstract]
Investments in securities	0	0
Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member] | Mutual Funds [Member]
Investments in securities [Abstract]
Investments in securities	0	0
Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member] | Closed-end Funds [Member]
Investments in securities [Abstract]
Investments in securities	$ 0	$ 0