Additional Milestone payments.

No definition available.

Name:	tsha_AdditionalMilestonePayments
Namespace Prefix:	tsha_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Clinical, regulatory and commercial milestones to be received.

+ References

No definition available.

+ Details

Name:	tsha_ClinicalRegulatoryAndCommercialMilestonesToBeReceived
Namespace Prefix:	tsha_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

License agreement commercial milestones payment.

+ References

No definition available.

+ Details

Name:	tsha_LicenseAgreementCommercialMilestonesPayment
Namespace Prefix:	tsha_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

License agreement regulatory milestones payment.

+ References

No definition available.

+ Details

Name:	tsha_LicenseAgreementRegulatoryMilestonesPayment
Namespace Prefix:	tsha_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

License and inventory purchase agreement regulatory related milestones payment.

+ References

No definition available.

+ Details

Name:	tsha_LicenseAndInventoryPurchaseAgreementRegulatoryRelatedMilestonesPayment
Namespace Prefix:	tsha_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

License and inventory purchase agreement sales related milestones payment.

+ References

No definition available.

+ Details

Name:	tsha_LicenseAndInventoryPurchaseAgreementSalesRelatedMilestonesPayment
Namespace Prefix:	tsha_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Minimum licensed product to develop obtain regulatory approval for and commercialize.

+ References

No definition available.

+ Details

Name:	tsha_MinimumLicensedProductToDevelopObtainRegulatoryApprovalForAndCommercialize
Namespace Prefix:	tsha_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Payment of license fee.

+ References

No definition available.

+ Details

Name:	tsha_PaymentOfLicenseFee
Namespace Prefix:	tsha_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Payment of one-time upfront license fee.

+ References

No definition available.

+ Details

Name:	tsha_PaymentOfOneTimeUpfrontLicenseFee
Namespace Prefix:	tsha_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Payments to acquire license right.

+ References

No definition available.

+ Details

Name:	tsha_PaymentsToAcquireLicenseRight
Namespace Prefix:	tsha_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Percentage of common stock shares entitled to receive additional shares on fully diluted basis.

+ References

No definition available.

+ Details

Name:	tsha_PercentageOfCommonStockSharesEntitledToReceiveAdditionalSharesOnFullyDilutedBasis
Namespace Prefix:	tsha_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of fully diluted common stock shares outstanding.

+ References

No definition available.

+ Details

Name:	tsha_PercentageOfFullyDilutedCommonStockSharesOutstanding
Namespace Prefix:	tsha_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Preclinical activities period under sponsored research agreements.

+ References

No definition available.

+ Details

Name:	tsha_PreclinicalActivitiesPeriodUnderSponsoredResearchAgreements
Namespace Prefix:	tsha_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Purchase of clinical materials and reimbursement incurred development costs.

+ References

No definition available.

+ Details

Name:	tsha_PurchaseOfClinicalMaterialsAndReimbursementIncurredDevelopmentCosts
Namespace Prefix:	tsha_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Regulatory related milestones obligation payable.

+ References

No definition available.

+ Details

Name:	tsha_RegulatoryRelatedMilestonesObligationPayable
Namespace Prefix:	tsha_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Research grant of committed fund amount.

+ References

No definition available.

+ Details

Name:	tsha_ResearchGrantOfCommittedFundAmount
Namespace Prefix:	tsha_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Research grant outstanding fund amount.

+ References

No definition available.

+ Details

Name:	tsha_ResearchGrantOutstandingFundAmount
Namespace Prefix:	tsha_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Sale-related milestones per licensed product and royalties on net sales of licensed products payable.

+ References

No definition available.

+ Details

Name:	tsha_SaleRelatedMilestonesPerLicensedProductAndRoyaltiesOnNetSalesOfLicensedProductsPayable
Namespace Prefix:	tsha_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Upfront payment.

+ References

No definition available.

+ Details

Name:	tsha_UpfrontPayment
Namespace Prefix:	tsha_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

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

- Definition

Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_CommonStockSharesIssued
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

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

- Definition

The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 912
-SubTopic 730
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6472174&loc=d3e58812-109433

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 985
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6501960&loc=d3e128462-111756

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 730
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6420194&loc=d3e21568-108373

+ Details

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

- Details

Name:	us-gaap_TypeOfArrangementAxis=tsha_AcquisitionOfWorldwideRightsForTSHA120ForTreatmentOfGiantAxonalNeuropathyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CounterpartyNameAxis=tsha_UTSouthwesternAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CounterpartyNameAxis=tsha_QueensAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementLocationAxis=us-gaap_ResearchAndDevelopmentExpenseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	srt_CounterpartyNameAxis=tsha_AbeonaCLN1AgreementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CounterpartyNameAxis=tsha_AbeonaTherapeuticsIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=tsha_AbeonaRettAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Research, Collaboration and License Agreements - Additional Information (Details)	1 Months Ended					3 Months Ended			9 Months Ended		12 Months Ended
	Mar. 31, 2021 USD ($)	Oct. 31, 2020 USD ($)	Aug. 31, 2020 USD ($)	Apr. 30, 2020 Product	Dec. 31, 2019 USD ($)	Sep. 30, 2021 USD ($) shares	Sep. 30, 2020 USD ($)	Mar. 31, 2020 USD ($) shares	Sep. 30, 2021 USD ($) shares	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($) shares	Aug. 12, 2021	Oct. 29, 2020 USD ($)	Feb. 21, 2020 USD ($)	Nov. 30, 2019 shares
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Common stock, shares issued \| shares						38,473,945			38,473,945		37,761,435
Percentage of interest rate												7.00%
Research and development						$ 39,528,000	$ 11,057,000		$ 94,025,000	$ 19,633,000
TSHA-120
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Additional milestone payments									0
Research and development	$ 5,500,000
Upfront payment	5,500,000
Clinical, regulatory and commercial milestones to be received	$ 19,300,000
UT Southwestern Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Preclinical activities period under sponsored research agreements				2 years
Minimum licensed product to develop obtain regulatory approval for and commercialize \| Product				1
Common stock, shares issued \| shares								0							2,179,000
Percentage of fully diluted common stock shares outstanding															20.00%
Percentage of entitled to receive additional shares on fully diluted basis															10.00%
Queen's Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research grant of committed fund amount					$ 3,800,000
Percentage of interest rate					6.00%
Research grant outstanding fund amount											$ 0
Additional milestone payments									0
Queen's Agreement \| Research and Development Expense
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Cash payment to acquire license agreement								$ 3,000,000.0
Queen's Agreement \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License agreement regulatory milestones payment														$ 10,000,000.0
License agreement commercial milestones payment														$ 10,000,000.0
Abeona CLN1 Agreements
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Additional milestone payments									0
License fee payment			$ 3,000,000.0
Purchase of clinical materials and reimbursement incurred development costs		$ 4,000,000.0
Research and development											7,000,000.0
Abeona CLN1 Agreements \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License and inventory purchase agreement regulatory related milestones payment			26,000,000.0
License and inventory purchase agreement sales related milestones payment			$ 30,000,000.0
Abeona \| Abeona Rett Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Additional milestone payments									$ 0
Payment of one-time upfront license fee											$ 3,000,000.0
Abeona \| Maximum \| Abeona Rett Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Regulatory related milestones obligation payable													$ 26,500,000
Sale-related milestones per licensed product and royalties on net sales of licensed products payable													$ 30,000,000.0