Fair Value (Details) - USD ($) $ in Thousands | Mar. 31, 2021 | Dec. 31, 2020 |
Investments in securities [Abstract] | | |
Investments in securities | $ 30,430 | $ 25,845 |
Securities sold, not yet purchased [Abstract] | | |
Total securities sold, not yet purchased | 0 | 799 |
Common Stocks [Member] | | |
Investments in securities [Abstract] | | |
Investments in securities | 19,068 | 19,099 |
Open-end Funds [Member] | | |
Investments in securities [Abstract] | | |
Investments in securities | 5,960 | 6,128 |
Actively Managed Semi-transparent EFTs [Member] | | |
Investments in securities [Abstract] | | |
Investments in securities | 4,890 | 0 |
Closed-end Funds [Member] | | |
Investments in securities [Abstract] | | |
Investments in securities | 512 | 618 |
Recurring Basis [Member] | | |
Assets [Abstract] | | |
Cash equivalents | 118,377 | 32,661 |
Investments in securities [Abstract] | | |
Investments in securities | 30,430 | 25,845 |
Total assets at fair value | 148,807 | 58,506 |
Securities sold, not yet purchased [Abstract] | | |
Trading - Common Stocks | | 799 |
Total securities sold, not yet purchased | | 799 |
Recurring Basis [Member] | Common Stocks [Member] | | |
Investments in securities [Abstract] | | |
Investments in securities | 19,068 | 19,099 |
Recurring Basis [Member] | Open-end Funds [Member] | | |
Investments in securities [Abstract] | | |
Investments in securities | 5,960 | 6,128 |
Recurring Basis [Member] | Actively Managed Semi-transparent EFTs [Member] | | |
Investments in securities [Abstract] | | |
Investments in securities | 4,890 | |
Recurring Basis [Member] | Closed-end Funds [Member] | | |
Investments in securities [Abstract] | | |
Investments in securities | 512 | 618 |
Recurring Basis [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | | |
Assets [Abstract] | | |
Cash equivalents | 118,377 | 32,661 |
Investments in securities [Abstract] | | |
Investments in securities | 30,430 | 25,845 |
Total assets at fair value | 148,807 | 58,506 |
Securities sold, not yet purchased [Abstract] | | |
Trading - Common Stocks | | 799 |
Total securities sold, not yet purchased | | 799 |
Recurring Basis [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Common Stocks [Member] | | |
Investments in securities [Abstract] | | |
Investments in securities | 19,068 | 19,099 |
Recurring Basis [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Open-end Funds [Member] | | |
Investments in securities [Abstract] | | |
Investments in securities | 5,960 | 6,128 |
Recurring Basis [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Actively Managed Semi-transparent EFTs [Member] | | |
Investments in securities [Abstract] | | |
Investments in securities | 4,890 | |
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 | 512 | 618 |
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 |
Securities sold, not yet purchased [Abstract] | | |
Trading - Common Stocks | | 0 |
Total securities sold, not yet purchased | | 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] | Open-end Funds [Member] | | |
Investments in securities [Abstract] | | |
Investments in securities | 0 | 0 |
Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | Actively Managed Semi-transparent EFTs [Member] | | |
Investments in securities [Abstract] | | |
Investments in securities | 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 |
Securities sold, not yet purchased [Abstract] | | |
Trading - Common Stocks | | 0 |
Total securities sold, not yet purchased | | 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] | Open-end Funds [Member] | | |
Investments in securities [Abstract] | | |
Investments in securities | 0 | 0 |
Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member] | Actively Managed Semi-transparent EFTs [Member] | | |
Investments in securities [Abstract] | | |
Investments in securities | 0 | |
Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member] | Closed-end Funds [Member] | | |
Investments in securities [Abstract] | | |
Investments in securities | $ 0 | $ 0 |