Percentage of revenue, fees and commissions earned from transactions between (a) a parent company and its subsidiaries; (b) subsidiaries of a common parent; (c) an entity and trusts for the benefit of employees, for example, but not limited to, pension and profit-sharing trusts that are managed by or under the trusteeship of the entity's management; (d) an entity and its principal, owners, management, or members of their immediate families; and (e) affiliates.

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Represents the total of interest and dividend income, including any amortization and accretion (as applicable) of discounts and premiums, earned from (1) loans and leases whether held-for-sale or held-in-portfolio; (2) investment securities; (3) federal funds sold; (4) securities purchased under agreements to resell; (5) investments in banker's acceptances, commercial paper, or certificates of deposit; (6) dividend income; or (7) other investments not otherwise specified herein.

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-Publisher FASB
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Sum of the carrying amounts as of the balance sheet date of all investments.

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-Publisher FASB
-Name Accounting Standards Codification
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Amount of revenue, fees and commissions earned from transactions between (a) a parent company and its subsidiaries; (b) subsidiaries of a common parent; (c) an entity and trusts for the benefit of employees, for example, but not limited to, pension and profit-sharing trusts that are managed by or under the trusteeship of the entity's management; (d) an entity and its principal, owners, management, or members of their immediate families; and (e) affiliates.

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-Topic 470
-SubTopic 10
-Section S99
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Related Party Transactions (Details) - USD ($)	3 Months Ended			6 Months Ended
Related Party Transactions (Details) - USD ($)	Jun. 30, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Related Party Transactions [Abstract]
Investment income	$ 3,377	$ 11,833		$ 12,363	$ 48,089
Underwriting and Sales Manager Fees [Member]
Related Party Transactions [Abstract]
Revenue from related party transactions			$ 30,488
Gabelli Funds, LLC [Member] \| Gabelli U.S. Treasury Money Market Fund [Member]
Related Party Transactions [Abstract]
Affiliated investments	3,250,673			3,250,673		$ 4,724,290
Investment income	8	5,909		125	35,459
Affiliated Entities [Member] \| Commissions [Member]
Related Party Transactions [Abstract]
Revenue from related party transactions	$ 292,731	$ 789,875		$ 664,981	$ 1,481,659
Revenue percentage	52.00%	72.00%		54.00%	67.00%
GAMCO Global Gold, Natural Resources & Income Trust ("GGN") [Member] \| Sales Manager Fees [Member]
Related Party Transactions [Abstract]
Revenue from related party transactions	$ 0	$ 0		$ 0	$ 334,825