Related Party Transactions	3 Months Ended
Mar. 31, 2020
Related Party Transactions [Abstract]
Related Party Transactions	3. Related Party Transactions At March 31, 2020 and December 31, 2019, the Company had an investment of $5,661,750 and $6,579,577, respectively, in The Gabelli U.S. Treasury Money Market Fund advised by Gabelli Funds, LLC, which is an affiliate of the Company. The amount is recorded in cash and cash equivalents in the Condensed Consolidated Statements of Financial Condition. Income earned from this investment totaled $29,550 and $59,035 for the three months ended March 31, 2020 and 2019, respectively, and is included in dividends and interest revenues in the Condensed Consolidated Statements of Operations. For the three months ended March 31, 2020 and 2019, the Company earned $691,784 and $1,132,845, or approximately 67% and 74%, respectively, of its commission revenue from transactions executed on behalf of funds advised by Gabelli Funds, LLC. (“Gabelli Funds”) and private wealth management clients advised by GAMCO Asset Management Inc., (“GAMCO Asset”), each affiliates of the Company. GAMCO Asset and Gabelli Funds paid a total of $377,500 to the Company pursuant to research services agreements (see Note 2) for the three months ended March 31, 2019. No amounts for such services were paid during the three months ended March 31, 2020. These agreements were terminated effective January 1, 2020. The Company participated as agent in the secondary offerings of the GAMCO Global Gold, Natural Resources & Income Trust (“GGN”). Pursuant to sales agreements between the parties, the Company earned sales manager fees related to this offering of $334,825 and $0 during the three months ended March 31, 2020 and 2019, respectively. Sales manager fees are separately disclosed in the Condensed Consolidated Statements of Operations. The Company participated in the secondary offerings of the preferred stock of affiliated closed end funds in December 2019. The final settlements were received during March 2020 resulting in additional underwriting profit of $30,488. The Company pays AC a management fee equal to 20% of the Company’s year-to-date pretax profits before consideration of this fee. In the three months ended March 31, 2020 and 2019, the Company did not pay a management fee to AC as there were no pretax profits. AC has a sublease agreement with GBL that expired on April 1, 2020 and continues on a month to month basis. AC allocates this expense to the Company based on the percentage of square footage occupied by the Company’s employees (including pro rata allocation of common space). For the three months ended March 31, 2020 and 2019, the Company paid $27,113 and $82,913, respectively, to AC. These amounts are included within occupancy and equipment expenses on the Condensed Consolidated Statements of Operations.

3. Related Party Transactions

At March 31, 2020 and December 31, 2019, the Company had an investment of $5,661,750 and $6,579,577, respectively, in The Gabelli U.S. Treasury Money Market Fund advised by Gabelli Funds, LLC, which is an affiliate of the Company. The amount is recorded in cash and cash equivalents in the Condensed Consolidated Statements of Financial Condition. Income earned from this investment totaled $29,550 and $59,035 for the three months ended March 31, 2020 and 2019, respectively, and is included in dividends and interest revenues in the Condensed Consolidated Statements of Operations.

For the three months ended March 31, 2020 and 2019, the Company earned $691,784 and $1,132,845, or approximately 67% and 74%, respectively, of its commission revenue from transactions executed on behalf of funds advised by Gabelli Funds, LLC. (“Gabelli Funds”) and private wealth management clients advised by GAMCO Asset Management Inc., (“GAMCO Asset”), each affiliates of the Company. GAMCO Asset and Gabelli Funds paid a total of $377,500 to the Company pursuant to research services agreements (see Note 2) for the three months ended March 31, 2019. No amounts for such services were paid during the three months ended March 31, 2020. These agreements were terminated effective January 1, 2020.

The Company participated as agent in the secondary offerings of the GAMCO Global Gold, Natural Resources & Income Trust (“GGN”). Pursuant to sales agreements between the parties, the Company earned sales manager fees related to this offering of $334,825 and $0 during the three months ended March 31, 2020 and 2019, respectively. Sales manager fees are separately disclosed in the Condensed Consolidated Statements of Operations.

The Company participated in the secondary offerings of the preferred stock of affiliated closed end funds in December 2019. The final settlements were received during March 2020 resulting in additional underwriting profit of $30,488.

The Company pays AC a management fee equal to 20% of the Company’s year-to-date pretax profits before consideration of this fee. In the three months ended March 31, 2020 and 2019, the Company did not pay a management fee to AC as there were no pretax profits.

AC has a sublease agreement with GBL that expired on April 1, 2020 and continues on a month to month basis. AC allocates this expense to the Company based on the percentage of square footage occupied by the Company’s employees (including pro rata allocation of common space). For the three months ended March 31, 2020 and 2019, the Company paid $27,113 and $82,913, respectively, to AC. These amounts are included within occupancy and equipment expenses on the Condensed Consolidated Statements of Operations.