Quarterly report pursuant to Section 13 or 15(d)

Cover
- Document and Entity Information
Financial Statements
Notes to Financial Statements
Accounting Policies
- Summary of Significant Accounting Policies (Policies)
Notes Tables
Notes Details

CONSOLIDATED SCHEDULE OF PORTFOLIO INVESTMENTS (Unaudited) (Parenthetical)

v3.23.2

CONSOLIDATED SCHEDULE OF PORTFOLIO INVESTMENTS (Unaudited) (Parenthetical) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2023	Dec. 31, 2022
Schedule of Investments [Line Items]
Percentage of fair value level 3 investments	89.00%	90.00%
Investment at Cost	$ 60,969,018	$ 55,716,237
Interest due from investments	$ 50,000	$ 50,000
Blocker corporation
Schedule of Investments [Line Items]
Equity owned percentage	100.00%	100.00%
Fair Value
Schedule of Investments [Line Items]
Investment at Cost	$ 61,000,000.0	$ 55,700,000
Net unrealized appreciation	5,800,000	5,800,000
Unrealized appreciation of investment securities	13,600,000	13,500,000
Unrealized depreciation of investment securities	7,800,000	7,700,000
Aggregate gross unrealized gain for federal income tax	13,600,000	13,200,000
Aggregate gross unrealized loss for federal income tax	6,900,000	6,700,000
Net unrealized gain for federal income tax	6,700,000	6,500,000
Tax cost	$ 60,500,000	$ 55,000,000.0
Minimum
Schedule of Investments [Line Items]
Percentage of voting securities	5.00%	5.00%
Percentage of board representation	50.00%	50.00%
Maximum
Schedule of Investments [Line Items]
Percentage of voting securities	25.00%	25.00%

- Definition

Gross unrealized gain for federal income tax.

+ References

No definition available.

+ Details

Name:	rand_GrossUnrealizedGainForFederalIncomeTax
Namespace Prefix:	rand_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Gross unrealized loss for federal income tax.

+ References

No definition available.

+ Details

Name:	rand_GrossUnrealizedLossForFederalIncomeTax
Namespace Prefix:	rand_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Interest due from investments.

+ References

No definition available.

+ Details

Name:	rand_InterestDueFromInvestments
Namespace Prefix:	rand_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Net unrealized gain for federal income taxes.

+ References

No definition available.

+ Details

Name:	rand_NetUnrealizedGainForFederalIncomeTaxes
Namespace Prefix:	rand_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Percentage of board representation.

+ References

No definition available.

+ Details

Name:	rand_PercentageOfBoardRepresentation
Namespace Prefix:	rand_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of fair value level 3 investments.

+ References

No definition available.

+ Details

Name:	rand_PercentageOfFairValueLevel3Investments
Namespace Prefix:	rand_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of voting securities.

+ References

No definition available.

+ Details

Name:	rand_PercentageOfVotingSecurities
Namespace Prefix:	rand_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI https://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

+ Details

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Cost of the investment.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 210
-Section 50
-Paragraph 6
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=99383244&loc=d3e12121-115841

+ Details

Name:	us-gaap_InvestmentOwnedAtCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This element represents the excess of the cost (face amount, notional amount) of an investment (security, contract) over its fair value which deficiency has not been recognized in earnings of the entity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 320
-Section S99
-Paragraph 22
-URI https://asc.fasb.org/extlink&oid=122147990&loc=SL6090603-123010

+ Details

Name:	us-gaap_InvestmentOwnedUnrecognizedUnrealizedAppreciation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This element represents the net excess or deficiency of the fair value of an investment (security, contract) over or under its cost (face amount, notional amount), respectively, which excess value or deficiency has not been recognized in earnings of the entity.

+ References

+ Details

Name:	us-gaap_InvestmentOwnedUnrecognizedUnrealizedAppreciationDepreciationNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

+ References

+ Details

Name:	us-gaap_InvestmentOwnedUnrecognizedUnrealizedDepreciation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_ScheduleOfInvestmentsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The aggregate cost of investments for Federal income tax purposes.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 10
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-03(h)(2)(iv))
-URI https://asc.fasb.org/extlink&oid=126898976&loc=d3e600178-122990

+ Details

Name:	us-gaap_TaxBasisOfInvestmentsCostForIncomeTaxPurposes
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=rand_BlockerCorporationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByMeasurementBasisAxis=us-gaap_EstimateOfFairValueFairValueDisclosureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: