Commitments and Contingencies - Additional Information (Details) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2025 USD ($) Equipment	Mar. 31, 2024 USD ($)	Dec. 31, 2024 USD ($) Equipment
Commitments And Contingencies [Line Items]
Outstanding refunded commitments	$ 49.7		$ 31.2
Number of portfolio companies unfunded commitments \| Equipment	4		2
Total lease expense	$ 0.4	$ 0.3
Right of use asset	$ 5.2		$ 5.4
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Other Assets		Other Assets
Lease liability	$ 5.5		$ 5.7
Operating Lease, Liability, Statement of Financial Position [Extensible Enumeration]	Accounts Payable And Other Accrued Liabilities		Accounts Payable And Other Accrued Liabilities
EPT 16 LLC
Commitments And Contingencies [Line Items]
Outstanding refunded commitments	$ 0.8		$ 0.8
Capital commitments	10.0
Unfunded capital commitment	0.8	$ 0.8
JV Partner
Commitments And Contingencies [Line Items]
Outstanding refunded commitments	3.0		$ 3.0
Capital commitments	$ 21.4
San Diego Office
Commitments And Contingencies [Line Items]
Lease commencement period	Mar. 10, 2023
Lease expiration period	Jan. 31, 2026
Second lease commencement period	Jun. 01, 2024
Second lease expiration period	Nov. 14, 2025
Remaining lease term	5 years 10 months 24 days
Discount rates	8.54%		8.53%
Phoenix Office
Commitments And Contingencies [Line Items]
Lease commencement period	Jul. 10, 2021
Lease extension date	May 31, 2031
Lease expiration period	Sep. 17, 2024

Commitments and contingencies.

No definition available.

Name:	trin_CommitmentsAndContingenciesLineItems
Namespace Prefix:	trin_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Lease commencement period.

+ References

No definition available.

+ Details

Name:	trin_LeaseCommencementPeriod
Namespace Prefix:	trin_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Lease expiration period.

+ References

No definition available.

+ Details

Name:	trin_LeaseExpirationPeriod
Namespace Prefix:	trin_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Lease extension date.

+ References

No definition available.

+ Details

Name:	trin_LeaseExtensionDate
Namespace Prefix:	trin_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of portfolio unfunded commitments.

+ References

No definition available.

+ Details

Name:	trin_NumberOfPortfolioUnfundedCommitments
Namespace Prefix:	trin_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Second lease commencement period.

+ References

No definition available.

+ Details

Name:	trin_SecondLeaseCommencementPeriod
Namespace Prefix:	trin_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Second lease expiration period.

+ References

No definition available.

+ Details

Name:	trin_SecondLeaseExpirationPeriod
Namespace Prefix:	trin_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Unfunded capital commitment.

+ References

No definition available.

+ Details

Name:	trin_UnfundedCapitalCommitment
Namespace Prefix:	trin_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Fair value portion of arrangements with third parties, including, but not limited to, operating lease arrangement and arrangement in which the entity has agreed to expend funds to procure goods or services, or has agreed to commit resources to supply goods or services.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2E
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2E

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(25))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

+ Details

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

- Definition

Amount of funds committed to investment company from investors.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 205
-Name Accounting Standards Codification
-Section 50
-Paragraph 25
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478494/946-205-50-25

+ Details

Name:	us-gaap_InvestmentCompanyCommittedCapital
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Discount rate used by lessee to determine present value of operating lease payments.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478964/842-20-50-3

+ Details

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

- Definition

Remaining lease term of operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 7A
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478964/842-20-50-7A

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478964/842-20-50-3

+ Details

Name:	us-gaap_LesseeOperatingLeaseRemainingLeaseTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of operating lease expense. Excludes sublease income.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 4
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479041/842-20-45-4

+ Details

Name:	us-gaap_OperatingLeaseExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Present value of lessee's discounted obligation for lease payments from operating lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479041/842-20-45-1

+ Details

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

- Definition

Indicates line item in statement of financial position that includes operating lease liability.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479041/842-20-45-2

+ Details

Name:	us-gaap_OperatingLeaseLiabilityStatementOfFinancialPositionExtensibleList
Namespace Prefix:	us-gaap_
Data Type:	enum2:enumerationSetItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of lessee's right to use underlying asset under operating lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479041/842-20-45-1

+ Details

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

- Definition

Indicates line item in statement of financial position that includes operating lease right-of-use asset.

+ References

+ Details

Name:	us-gaap_OperatingLeaseRightOfUseAssetStatementOfFinancialPositionExtensibleList
Namespace Prefix:	us-gaap_
Data Type:	enum2:enumerationSetItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=trin_Ept16LlcMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=trin_JvPartnerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=trin_SanDiegoOfficeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=trin_PhoenixOfficeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: