Related Party Transactions (Q1) (Details) - USD ($)	3 Months Ended	12 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Related Party Transactions [Abstract]
Investment income	$ 36,256	$ 63,693	$ 194,955	$ 1,893,237
Underwriting and Sales Manager Fees [Member]
Related Party Transactions [Abstract]
Revenue from related party transactions	30,488		431,114	102,930
Gabelli Funds, LLC [Member] \| Gabelli U.S. Treasury Money Market Fund [Member]
Related Party Transactions [Abstract]
Affiliated investments	5,661,750		6,579,577	11,276,289
Investment income	29,550	59,035	175,846	157,581
Gabelli Funds, LLC [Member] \| Research Services [Member]
Related Party Transactions [Abstract]
Revenue from related party transactions	0	377,500	750,000	1,030,000
Affiliated Entities [Member] \| Commissions [Member]
Related Party Transactions [Abstract]
Revenue from related party transactions	$ 691,784	$ 1,132,845	$ 4,875,768	$ 3,825,998
Revenue percentage	67.00%	74.00%	76.00%	62.00%
GAMCO Asset Management Inc. [Member] \| Research Services [Member]
Related Party Transactions [Abstract]
Revenue from related party transactions	$ 0	$ 377,500	$ 752,550	$ 10,000,000
GAMCO Global Gold, Natural Resources & Income Trust ("GGN") [Member] \| Sales Manager Fees [Member]
Related Party Transactions [Abstract]
Revenue from related party transactions	$ 334,825	$ 0	$ 729,893	$ 15,616

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.

No definition available.

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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=116637391&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=119400593&loc=d3e572229-122910

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- References

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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=116637345&loc=SL114874292-224272

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-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=116634182&loc=SL114868664-224227

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