Additional payments that could be due by the Company upon achievement of certain milestones.

No definition available.

Name:	srra_AdditionalMilestonePayment
Namespace Prefix:	srra_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Aggregate amount of payments that could be due by the Company upon achievement of certain milestones.

+ References

No definition available.

+ Details

Name:	srra_AggregateAmountOfMilestonePayment
Namespace Prefix:	srra_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Upfront payment for asset purchase.

+ References

No definition available.

+ Details

Name:	srra_AssetPurchasePayment
Namespace Prefix:	srra_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Milestone payment payable upon achievement of a milestone.

+ References

No definition available.

+ Details

Name:	srra_MilestonePaymentAmount
Namespace Prefix:	srra_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Upfront fee received in connection with collaboration agreement.

+ References

No definition available.

+ Details

Name:	srra_UpfrontLicenseFeeReceived
Namespace Prefix:	srra_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Upfront license payment.

+ References

No definition available.

+ Details

Name:	srra_UpfrontLicensePayment
Namespace Prefix:	srra_
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_LossContingenciesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- 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://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 2: 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_RestructuringCostAndReserveAxis=srra_CarnaCollaborationAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PurchaseCommitmentExcludingLongtermCommitmentAxis=srra_AssetPurchaseAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PurchaseCommitmentExcludingLongtermCommitmentAxis=srra_AstraZenecaLicenseAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PurchaseCommitmentExcludingLongtermCommitmentAxis=srra_CPFLicenseAgreementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srra_PhaseAxis=srra_TransferOfPhase1ClinicalTrialsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srra_PhaseAxis=srra_FirstPatientFirstTrialPostAmendmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PurchaseCommitmentExcludingLongtermCommitmentAxis=srra_CPFLicenseAgreementAmendmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended				3 Months Ended		6 Months Ended
	Aug. 31, 2021	Aug. 31, 2018	Oct. 31, 2016	Jun. 30, 2016	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Nov. 30, 2020	Jan. 31, 2017
Loss Contingencies [Line Items]
Research and development					$ 14,149	$ 10,189	$ 28,102	$ 21,780
Carna Collaboration Agreement [Member]
Loss Contingencies [Line Items]
Upfront payment paid				$ 900
Upfront License Fee							300
Asset Purchase Agreement [Member]
Loss Contingencies [Line Items]
Upfront payment paid		$ 3,000
Aggregate milestone payment							190,000
AstraZeneca License Agreement [Member]
Loss Contingencies [Line Items]
Aggregate milestone payment	$ 208,000
Research and development	$ 8,000
CPF License Agreements [Member]
Loss Contingencies [Line Items]
Upfront payment paid			$ 7,000
Additional milestone payment payable							319,500
CPF License Agreements [Member] \| Transfer of Phase 1 Clinical Trials [Member]
Loss Contingencies [Line Items]
Milestone payment										$ 2,000
CPF License Agreements [Member] \| First patient first trial post amendment [Member]
Loss Contingencies [Line Items]
Milestone payment									$ 2,000
CPF License Agreement Amendment [Member]
Loss Contingencies [Line Items]
Additional milestone payment payable							$ 290,000