Related Party Transactions	12 Months Ended
Dec. 31, 2017
Related Party Transactions [Abstract]
Related Party Transactions	K. Related Party Transactions The following is a summary of certain related party transactions. GGCP Holdings LLC owns a majority of our Class B Stock, representing approximately 91% of the combined voting power and 63% of the outstanding shares of our common stock at December 31, 2017. AC and its subsidiaries, own 4.4 million shares of our Class A Stock, representing approximately 2% of the combined voting power and 15% of the outstanding shares of our common stock at December 31, 2017. Capital Lease We lease an approximately 60,000 square foot building located at 401 Theodore Fremd Avenue, Rye, New York as our headquarters (the “Building”) from an entity controlled by members of the Chairman’s family. See Notes H and I. We sub-lease approximately 3,300 square feet in the Building to LICT Corporation, a company for which Mr. Gabelli serves as Chairman and CEO, which pays rent at the rate of $28 per square foot plus $3 per square foot for electricity, subject to adjustment for increases in taxes and other operating expenses. The total amounts paid in 2017, 2016, and 2015 for rent and other expenses under this lease were $116,756, $116,564, and $119,686, respectively. Concurrent with the extension of the lease on the Building during 2008, we and LICT Corporation further agreed to extend the term of the sub-lease until December 2023 on the same terms and conditions. As of July 1, 2008, we also sub-lease approximately 1,600 square feet in the Building to Teton. Teton pays rent at the rate of $37.75 per square foot plus $3 per square foot for electricity, subject to adjustment for increases in taxes and other operating expenses. The total amount paid in 2017, 2016 and 2015 for rent and other expenses under this lease were $68,293, $68,205 and $69,632, respectively, and were recorded in other operating expenses as a credit on the consolidated statements of income. As of April 1, 2016, we lease approximately 15,000 square feet in the Building to AC. For the period of April 1, 2016 to March 31, 2017, AC paid rent at the rate of $21.62 per square foot plus $3 per square foot for electricity, subject to adjustment for increases in taxes and other operating expenses. Effective April 1, 2017, AC paid rent at the rate of $22.03 per square foot plus $3 per square foot for electricity. The total amount paid in 2017 and 2016 for rent and other expenses under this lease was $367,798 and $297,185 and was recorded in distribution fee and other income on the consolidated statements of income. Investment Advisory Services GAMCO has entered into agreements to provide advisory and administrative services to MJG Associates, Inc., which is wholly-owned by Mr. Gabelli, with respect to the private investment funds managed by them. Pursuant to such agreements, MJG Associates, Inc. paid GAMCO $10,000 (excluding reimbursement of expenses) for each of the years 2017, 2016, and 2015. For 2017, 2016 and 2015, Manhattan Partners I, L.P. and Manhattan Partners II, L.P., investment partnerships for which John Gabelli Inc., an entity owned by John Gabelli, a brother of the Company’s Chairman, is the general partner, paid GAMCO investment advisory fees in the amount of $9,851, $11,274 and $13,595, respectively. In addition, an entity in which Mr. John Gabelli’s wife is the sole shareholder, is the co-general partner of S.W.A.N. Partners, LP (“S.W.A.N.”). S.W.A.N. paid GAMCO investment advisory fees in the amount of $19,776, $18,206 and $20,406 for 2017, 2016 and 2015, respectively, and is included in investment advisory and incentive fees on the consolidated statements of income. Effective August 17, 2017, John Gabelli Inc. is no longer the general partner of Manhattan Partners I, L.P. or Manhattan Partners II, L.P. and the entity that John Gabelli’s wife is the sole shareholder in is no longer the co-general partner of S.W.A.N. The Company serves as the investment advisor for the Funds and earns advisory fees based on predetermined percentages of the average net assets of the Funds. In addition, G.distributors has entered into distribution agreements with each of the Funds. As principal distributor, G.distributors incurs certain promotional and distribution costs related to the sale of Fund shares, for which it receives a distribution fee from the Funds or reimbursement from the investment advisor. For 2017, 2016 and 2015, the Company received $39.7 million, $41.0 million and $47.7 million, respectively, in distributions fees. Advisory and distribution fees receivable from the Funds were approximately $30.4 million and $32.9 million at December 31, 2017 and 2016, respectively. Pursuant to an agreement between Gabelli & Company Investment Advisers, Inc. (“GCI”) (formerly called Gabelli Securities, Inc.) and Funds Advisor, Funds Advisor pays to GCI 90% of the net revenues received by Funds Advisor related to being the advisor to the SICAV. Net revenues are defined as gross advisory fees less expenses related to payouts and expenses of the SICAV paid by Funds Advisor. The amounts paid by Funds Advisor to GCI for 2017, 2016 and 2015 were $2.8 million, $2.7 million and $1.0 million, respectively, and are included in other operating expenses on the consolidated statements of income. Compensation Immediately preceding the Offering and in conjunction with the Reorganization, GBL and our Chairman and CEO entered into an employment agreement. This agreement was amended and approved by shareholders on November 30, 2007 and most recently re-approved by shareholders on May 6, 2011. Under the terms of this agreement and consistent with the firm’s practice since its inception in 1977, Mr. Gabelli will also continue receiving a percentage of revenues or net operating contribution, which are substantially derived from AUM, as compensation relating to or generated by the following activities: (i) managing or overseeing the management of various investment companies and partnerships, (ii) attracting mutual fund shareholders, (iii) attracting and managing Institutional and Private Wealth Management clients, and (iv) otherwise generating revenues for the Company. Such payments are made in a manner and at rates as agreed to from time to time by GAMCO, which rates have been and generally will be the same as those received by other professionals at GAMCO performing similar services. With respect to our Institutional and Private Wealth Management and mutual fund advisory business, we pay out up to 40% of the revenues or net operating contribution to the portfolio managers and marketing staff who introduce, service or generate such business, with payments involving the Institutional and Private Wealth Management accounts being typically based on revenues and payments involving the mutual funds being typically based on net operating contribution. Mr. Gabelli has agreed that while he is employed by us he will not provide investment management services outside of GAMCO, except for certain permitted accounts as defined under the agreement. The 2008 Employment Agreement may not be amended without the approval of the Compensation Committee and Mr. Gabelli. The Chairman and CEO receives compensation in the form of a management fee for managing the Company. Additionally, he earns compensation for acting as portfolio manager and/or attracting and providing client service to a large number of GAMCO's Institutional and Private Wealth Management clients, for creating and acting as portfolio manager of several open-end funds, for creating and acting as portfolio manager of the closed-end funds and for providing other services. On December 29, 2017, the Company issued $11.7 million of notes payable to certain executive officers and employees relating to compensation earned in 2017. $5.5 million of the notes are due on January 31, 2018 and $6.2 million are due on February 28, 2018. The notes are included in compensation payable on the consolidated statement of financial condition. Other On May 31, 2006, the Company entered into an Exchange and Standstill Agreement with Frederick J. Mancheski, a significant shareholder, pursuant to which, among other things, he agreed to exchange his 2,071,635 shares of Class B Stock, which he received on a pari passu basis with his investment in GGCP, for an equal number of shares of Class A Stock. The standstill agreement expired on May 31, 2016. Under the terms of the standstill agreement, Mr. Mancheski agreed, among other things, to vote his shares in favor of the nominees and positions advocated by the Board of Directors. As stated in the latest available Form 13D filed by Mr. Mancheski on July 2, 2015, he continues to exercise voting control over 1,705,974 shares of Class A Stock. For 2017, 2016, and 2015, we incurred variable costs (but not the fixed costs) of $328,000, $353,000, and $432,000, respectively, for actual usage relating to our use of aircraft in which GGCP owns the fractional interests. GBL and Teton entered into a transitional administrative and management service agreement in connection with the spin-off of Teton from GBL that formalized certain arrangements. Effective January 1, 2011, Teton and GBL renegotiated the terms of the sub-administration agreement from a flat 0.20% on the average net assets of the mutual funds managed by Teton to 0.20% on the first $370 million in average net assets, 0.12% on the next $630 million in average net assets and 0.10% on average net assets in excess of $1 billion, as compensation for providing mutual fund administration services. Additionally, Teton paid to GBL an administrative services fee of $25,000 per month from April 1, 2014 through September 30, 2016. The administrative services fee was reduced to $18,750 per month for October 1, 2016 through May 31, 2017, and further reduced to $4,167 per month for June 1, 2017 through December 31, 2017. During 2017, 2016 and 2015, there was $2.1 million, $2.0 million and $2.2 million, respectively, included in distribution fees and other income on the consolidated statements of income. Effective January 1, 2014, GAMCO and Funds Advisor each entered into a research services agreement with G.research, LLC, a wholly-owned subsidiary of GCI, for G.research, LLC to provide them with the same types of research services that it provides to its other clients. For the years ended December 31, 2017, 2016 and 2015, GAMCO paid G.research, LLC $2.3 million, $1.5 million and $0.7 million, respectively. For the years ended December 31, 2017, 2016 and 2015, Funds Advisor paid G.research, LLC $2.3 million, $1.5 million and $0.8 million, respectively. GBL and AC entered into a transitional administrative and management services agreement in connection with the Spin-off. The agreement calls for GBL to provide to AC certain services including but not limited to: accounting, financial reporting and consolidation services, including the services of a financial and operations principal; treasury services, including, without limitation, insurance and risk management services and administration of benefits; tax planning, tax return preparation, recordkeeping and reporting services; human resources, including but not limited to the sourcing of permanent and temporary employees as needed, recordkeeping, performance reviews and terminations; legal and compliance advice, including the services of a Chief Compliance Officer; technical/technology consulting; and operations and general administrative assistance, including office space, office equipment and furniture, payroll, procurement, and administrative personnel. In addition, AC will provide GBL with payroll services. All services provided under the agreement by GBL to AC or by AC to GBL will be charged at cost. The agreement is terminable by either party on 30 days’ prior written notice to the other party and has a term of twelve months. At December 31, 2014, GCI owed GBL a demand loan of $16 million bearing interest at 5.5% annually. On December 28, 2015, GCI repaid the demand loan in full plus accrued and unpaid interest. The interest paid by GCI to GBL during 2015 was $0.9 million. In connection with the spin-off of AC on November 30, 2015, the Company issued the AC 4% PIK Note. During 2017, 2016 and 2015, GBL recorded interest expense of $3.0 million, $7.7 million and $0.8 million, respectively. See Note F. Debt for further details. In connection with the Offer, the Company borrowed $35.0 million from GGCP, which was repaid in full during 2016. During 2016, GBL recorded interest expense of $415,000. See Note F. Debt for further details. On December 27, 2017, GBL borrowed $15 million from AC. The note bears interest at 1.6% and is due on February 28, 2018. During 2017, GBL recorded interst expense of $4,000. See Note F. Debt for further details. In connection with the issuance of the Convertible Note, GGCP deposited cash equal to the principal amount of the Note and six months interest into an escrow account established pursuant to an escrow agreement by and among GGCP, the Company, the Convertible Note holder and the escrow agent. The Company paid the annual costs of setting up the escrow account in the amount of $55,000 and will continue to pay them as long as the escrow account is open. The Company did not pay any fees to GGCP in connection with the funding of the escrow account. On September 30, 2017, in connection with an amendment to the Escrow Agreement and in exchange for approximately 53% of the assets in the escrow account, the Company paid GGCP $60 million. On November 21, 2017, the Company paid GGCP $53.1 million for the remaining 47% interest in the escrow account and used the entire balance in the escrow account, along with an additional $1.4 million, to repurchase the Convertible Note. See Note F. Debt for additional details.

K. Related Party Transactions

The following is a summary of certain related party transactions.

GGCP Holdings LLC owns a majority of our Class B Stock, representing approximately 91% of the combined voting power and 63% of the outstanding shares of our common stock at December 31, 2017.

AC and its subsidiaries, own 4.4 million shares of our Class A Stock, representing approximately 2% of the combined voting power and 15% of the outstanding shares of our common stock at December 31, 2017.

Capital Lease

We lease an approximately 60,000 square foot building located at 401 Theodore Fremd Avenue, Rye, New York as our headquarters (the “Building”) from an entity controlled by members of the Chairman’s family. See Notes H and I.

We sub-lease approximately 3,300 square feet in the Building to LICT Corporation, a company for which Mr. Gabelli serves as Chairman and CEO, which pays rent at the rate of $28 per square foot plus $3 per square foot for electricity, subject to adjustment for increases in taxes and other operating expenses. The total amounts paid in 2017, 2016, and 2015 for rent and other expenses under this lease were $116,756, $116,564, and $119,686, respectively. Concurrent with the extension of the lease on the Building during 2008, we and LICT Corporation further agreed to extend the term of the sub-lease until December 2023 on the same terms and conditions. As of July 1, 2008, we also sub-lease approximately 1,600 square feet in the Building to Teton. Teton pays rent at the rate of $37.75 per square foot plus $3 per square foot for electricity, subject to adjustment for increases in taxes and other operating expenses. The total amount paid in 2017, 2016 and 2015 for rent and other expenses under this lease were $68,293, $68,205 and $69,632, respectively, and were recorded in other operating expenses as a credit on the consolidated statements of income. As of April 1, 2016, we lease approximately 15,000 square feet in the Building to AC. For the period of April 1, 2016 to March 31, 2017, AC paid rent at the rate of $21.62 per square foot plus $3 per square foot for electricity, subject to adjustment for increases in taxes and other operating expenses. Effective April 1, 2017, AC paid rent at the rate of $22.03 per square foot plus $3 per square foot for electricity. The total amount paid in 2017 and 2016 for rent and other expenses under this lease was $367,798 and $297,185 and was recorded in distribution fee and other income on the consolidated statements of income.

Investment Advisory Services

GAMCO has entered into agreements to provide advisory and administrative services to MJG Associates, Inc., which is wholly-owned by Mr. Gabelli, with respect to the private investment funds managed by them. Pursuant to such agreements, MJG Associates, Inc. paid GAMCO $10,000 (excluding reimbursement of expenses) for each of the years 2017, 2016, and 2015. For 2017, 2016 and 2015, Manhattan Partners I, L.P. and Manhattan Partners II, L.P., investment partnerships for which John Gabelli Inc., an entity owned by John Gabelli, a brother of the Company’s Chairman, is the general partner, paid GAMCO investment advisory fees in the amount of $9,851, $11,274 and $13,595, respectively. In addition, an entity in which Mr. John Gabelli’s wife is the sole shareholder, is the co-general partner of S.W.A.N. Partners, LP (“S.W.A.N.”). S.W.A.N. paid GAMCO investment advisory fees in the amount of $19,776, $18,206 and $20,406 for 2017, 2016 and 2015, respectively, and is included in investment advisory and incentive fees on the consolidated statements of income. Effective August 17, 2017, John Gabelli Inc. is no longer the general partner of Manhattan Partners I, L.P. or Manhattan Partners II, L.P. and the entity that John Gabelli’s wife is the sole shareholder in is no longer the co-general partner of S.W.A.N.

The Company serves as the investment advisor for the Funds and earns advisory fees based on predetermined percentages of the average net assets of the Funds. In addition, G.distributors has entered into distribution agreements with each of the Funds. As principal distributor, G.distributors incurs certain promotional and distribution costs related to the sale of Fund shares, for which it receives a distribution fee from the Funds or reimbursement from the investment advisor. For 2017, 2016 and 2015, the Company received $39.7 million, $41.0 million and $47.7 million, respectively, in distributions fees. Advisory and distribution fees receivable from the Funds were approximately $30.4 million and $32.9 million at December 31, 2017 and 2016, respectively.

Pursuant to an agreement between Gabelli & Company Investment Advisers, Inc. (“GCI”) (formerly called Gabelli Securities, Inc.) and Funds Advisor, Funds Advisor pays to GCI 90% of the net revenues received by Funds Advisor related to being the advisor to the SICAV. Net revenues are defined as gross advisory fees less expenses related to payouts and expenses of the SICAV paid by Funds Advisor. The amounts paid by Funds Advisor to GCI for 2017, 2016 and 2015 were $2.8 million, $2.7 million and $1.0 million, respectively, and are included in other operating expenses on the consolidated statements of income.

Compensation

Immediately preceding the Offering and in conjunction with the Reorganization, GBL and our Chairman and CEO entered into an employment agreement. This agreement was amended and approved by shareholders on November 30, 2007 and most recently re-approved by shareholders on May 6, 2011.

Under the terms of this agreement and consistent with the firm’s practice since its inception in 1977, Mr. Gabelli will also continue receiving a percentage of revenues or net operating contribution, which are substantially derived from AUM, as compensation relating to or generated by the following activities: (i) managing or overseeing the management of various investment companies and partnerships, (ii) attracting mutual fund shareholders, (iii) attracting and managing Institutional and Private Wealth Management clients, and (iv) otherwise generating revenues for the Company. Such payments are made in a manner and at rates as agreed to from time to time by GAMCO, which rates have been and generally will be the same as those received by other professionals at GAMCO performing similar services. With respect to our Institutional and Private Wealth Management and mutual fund advisory business, we pay out up to 40% of the revenues or net operating contribution to the portfolio managers and marketing staff who introduce, service or generate such business, with payments involving the Institutional and Private Wealth Management accounts being typically based on revenues and payments involving the mutual funds being typically based on net operating contribution.

Mr. Gabelli has agreed that while he is employed by us he will not provide investment management services outside of GAMCO, except for certain permitted accounts as defined under the agreement. The 2008 Employment Agreement may not be amended without the approval of the Compensation Committee and Mr. Gabelli.

The Chairman and CEO receives compensation in the form of a management fee for managing the Company. Additionally, he earns compensation for acting as portfolio manager and/or attracting and providing client service to a large number of GAMCO's Institutional and Private Wealth Management clients, for creating and acting as portfolio manager of several open-end funds, for creating and acting as portfolio manager of the closed-end funds and for providing other services.

On December 29, 2017, the Company issued $11.7 million of notes payable to certain executive officers and employees relating to compensation earned in 2017. $5.5 million of the notes are due on January 31, 2018 and $6.2 million are due on February 28, 2018. The notes are included in compensation payable on the consolidated statement of financial condition.

Other

On May 31, 2006, the Company entered into an Exchange and Standstill Agreement with Frederick J. Mancheski, a significant shareholder, pursuant to which, among other things, he agreed to exchange his 2,071,635 shares of Class B Stock, which he received on a pari passu basis with his investment in GGCP, for an equal number of shares of Class A Stock. The standstill agreement expired on May 31, 2016. Under the terms of the standstill agreement, Mr. Mancheski agreed, among other things, to vote his shares in favor of the nominees and positions advocated by the Board of Directors. As stated in the latest available Form 13D filed by Mr. Mancheski on July 2, 2015, he continues to exercise voting control over 1,705,974 shares of Class A Stock.

For 2017, 2016, and 2015, we incurred variable costs (but not the fixed costs) of $328,000, $353,000, and $432,000, respectively, for actual usage relating to our use of aircraft in which GGCP owns the fractional interests.

GBL and Teton entered into a transitional administrative and management service agreement in connection with the spin-off of Teton from GBL that formalized certain arrangements. Effective January 1, 2011, Teton and GBL renegotiated the terms of the sub-administration agreement from a flat 0.20% on the average net assets of the mutual funds managed by Teton to 0.20% on the first $370 million in average net assets, 0.12% on the next $630 million in average net assets and 0.10% on average net assets in excess of $1 billion, as compensation for providing mutual fund administration services. Additionally, Teton paid to GBL an administrative services fee of $25,000 per month from April 1, 2014 through September 30, 2016. The administrative services fee was reduced to $18,750 per month for October 1, 2016 through May 31, 2017, and further reduced to $4,167 per month for June 1, 2017 through December 31, 2017. During 2017, 2016 and 2015, there was $2.1 million, $2.0 million and $2.2 million, respectively, included in distribution fees and other income on the consolidated statements of income.

Effective January 1, 2014, GAMCO and Funds Advisor each entered into a research services agreement with G.research, LLC, a wholly-owned subsidiary of GCI, for G.research, LLC to provide them with the same types of research services that it provides to its other clients. For the years ended December 31, 2017, 2016 and 2015, GAMCO paid G.research, LLC $2.3 million, $1.5 million and $0.7 million, respectively. For the years ended December 31, 2017, 2016 and 2015, Funds Advisor paid G.research, LLC $2.3 million, $1.5 million and $0.8 million, respectively.

GBL and AC entered into a transitional administrative and management services agreement in connection with the Spin-off. The agreement calls for GBL to provide to AC certain services including but not limited to: accounting, financial reporting and consolidation services, including the services of a financial and operations principal; treasury services, including, without limitation, insurance and risk management services and administration of benefits; tax planning, tax return preparation, recordkeeping and reporting services; human resources, including but not limited to the sourcing of permanent and temporary employees as needed, recordkeeping, performance reviews and terminations; legal and compliance advice, including the services of a Chief Compliance Officer; technical/technology consulting; and operations and general administrative assistance, including office space, office equipment and furniture, payroll, procurement, and administrative personnel. In addition, AC will provide GBL with payroll services. All services provided under the agreement by GBL to AC or by AC to GBL will be charged at cost. The agreement is terminable by either party on 30 days’ prior written notice to the other party and has a term of twelve months.

At December 31, 2014, GCI owed GBL a demand loan of $16 million bearing interest at 5.5% annually. On December 28, 2015, GCI repaid the demand loan in full plus accrued and unpaid interest. The interest paid by GCI to GBL during 2015 was $0.9 million.

In connection with the spin-off of AC on November 30, 2015, the Company issued the AC 4% PIK Note. During 2017, 2016 and 2015, GBL recorded interest expense of $3.0 million, $7.7 million and $0.8 million, respectively. See Note F. Debt for further details.

In connection with the Offer, the Company borrowed $35.0 million from GGCP, which was repaid in full during 2016. During 2016, GBL recorded interest expense of $415,000. See Note F. Debt for further details.

On December 27, 2017, GBL borrowed $15 million from AC. The note bears interest at 1.6% and is due on February 28, 2018. During 2017, GBL recorded interst expense of $4,000. See Note F. Debt for further details.

In connection with the issuance of the Convertible Note, GGCP deposited cash equal to the principal amount of the Note and six months interest into an escrow account established pursuant to an escrow agreement by and among GGCP, the Company, the Convertible Note holder and the escrow agent. The Company paid the annual costs of setting up the escrow account in the amount of $55,000 and will continue to pay them as long as the escrow account is open. The Company did not pay any fees to GGCP in connection with the funding of the escrow account. On September 30, 2017, in connection with an amendment to the Escrow Agreement and in exchange for approximately 53% of the assets in the escrow account, the Company paid GGCP $60 million. On November 21, 2017, the Company paid GGCP $53.1 million for the remaining 47% interest in the escrow account and used the entire balance in the escrow account, along with an additional $1.4 million, to repurchase the Convertible Note. See Note F. Debt for additional details.