Investment in Securities, Investment in Equity Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Investments in Equity Securities and Funds [Abstract]
Cost	$ 44,814	$ 47,726
Estimated Fair Value	29,561	25,845
Common Stock [Member]
Investments in Equity Securities and Funds [Abstract]
Cost	33,652	41,341
Estimated Fair Value	17,687	19,099
Open-end Funds [Member]
Investments in Equity Securities and Funds [Abstract]
Cost	5,633	5,757
Estimated Fair Value	6,018	6,128
Actively Managed Semi-transparent EFTs [Member]
Investments in Equity Securities and Funds [Abstract]
Cost	5,000	0
Estimated Fair Value	5,320	0
Closed-end Funds [Member]
Investments in Equity Securities and Funds [Abstract]
Cost	523	628
Estimated Fair Value	529	618
Other [Member]
Investments in Equity Securities and Funds [Abstract]
Cost	6	0
Estimated Fair Value	$ 7	$ 0