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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.1-5)
-URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1(h))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

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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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07.1(c))
-URI http://asc.fasb.org/extlink&oid=120401555&loc=SL114874292-224272

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1(e))
-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227

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Related Party Transactions (Details) - USD ($)	3 Months Ended		6 Months Ended
Related Party Transactions (Details) - USD ($)	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Related Party Transactions [Abstract]
Investment income	$ 11,833	$ 58,085	$ 48,089	$ 121,778
Underwriting and Sales Manager Fees [Member]
Related Party Transactions [Abstract]
Revenue from related party transactions	0		30,488
Gabelli Funds, LLC [Member] \| Gabelli U.S. Treasury Money Market Fund [Member]
Related Party Transactions [Abstract]
Affiliated investments	4,938,005		4,938,005		$ 6,579,577
Investment income	5,909	53,464	35,459	112,499
Gabelli Funds, LLC [Member] \| Research Services [Member]
Related Party Transactions [Abstract]
Revenue from related party transactions			0	752,500
Affiliated Entities [Member] \| Commissions [Member]
Related Party Transactions [Abstract]
Revenue from related party transactions	$ 789,875	$ 1,154,633	$ 1,481,659	$ 2,287,478
Revenue percentage	72.00%	77.00%	69.00%	75.00%
GAMCO Asset Management Inc. [Member] \| Research Services [Member]
Related Party Transactions [Abstract]
Revenue from related party transactions	$ 0	$ 375,000
GAMCO Global Gold, Natural Resources & Income Trust ("GGN") [Member] \| Sales Manager Fees [Member]
Related Party Transactions [Abstract]
Revenue from related party transactions	$ 0	$ 122,571	$ 334,825	$ 122,571