Contract with Customer, Expiration Period

No definition available.

Name:	surf_ContractWithCustomerExpirationPeriod
Namespace Prefix:	surf_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Contract with Customer, Liability, Additional Payments to be Received

+ References

No definition available.

+ Details

Name:	surf_ContractWithCustomerLiabilityAdditionalPaymentsToBeReceived
Namespace Prefix:	surf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contract With Customer, Transaction Price

+ References

No definition available.

+ Details

Name:	surf_ContractWithCustomerTransactionPrice
Namespace Prefix:	surf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contract with Customer, Upfront Payment

+ References

No definition available.

+ Details

Name:	surf_ContractWithCustomerUpfrontPayment
Namespace Prefix:	surf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contract With Customer, Upfront Payments, Milestone Payments, Option Purchase Payments, Aggregate Amount

+ References

No definition available.

+ Details

Name:	surf_ContractWithCustomerUpfrontPaymentsMilestonePaymentsOptionPurchasePaymentsAggregateAmount
Namespace Prefix:	surf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Potential milestones payment.

+ References

No definition available.

+ Details

Name:	surf_PotentialMilestonesPayment
Namespace Prefix:	surf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Revenue, Number of Performance Obligations

+ References

No definition available.

+ Details

Name:	surf_RevenueNumberOfPerformanceObligations
Namespace Prefix:	surf_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Revenue, Performance Obligation, Number of Targets

+ References

No definition available.

+ Details

Name:	surf_RevenuePerformanceObligationNumberOfTargets
Namespace Prefix:	surf_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Revenue, Performance Obligation, Number of Targets Purchased

+ References

No definition available.

+ Details

Name:	surf_RevenuePerformanceObligationNumberOfTargetsPurchased
Namespace Prefix:	surf_
Data Type:	xbrli:integerItemType
Balance Type:	na
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

Amount of revenue from collaborative arrangement. Excludes revenue from contract with customer under Topic 606.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 808
-SubTopic 10
-Section 45
-Paragraph 3
-URI https://asc.fasb.org/extlink&oid=126928961&loc=SL5834089-161433

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 808
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=6931272&loc=SL5834143-161434

+ Details

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

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8906-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 40
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e9031-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 41
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e9038-108599

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8933-108599

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8933-108599

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130543-203045

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8736-108599

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8736-108599

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 42
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e9054-108599

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130545-203045

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 924
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 11.L)
-URI https://asc.fasb.org/extlink&oid=6472922&loc=d3e499488-122856

+ Details

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

- Details

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

- Details

Name:	srt_ProductOrServiceAxis=us-gaap_LicenseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TimingOfTransferOfGoodOrServiceAxis=us-gaap_TransferredAtPointInTimeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TimingOfTransferOfGoodOrServiceAxis=us-gaap_TransferredOverTimeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ProductOrServiceAxis=surf_TransitionServicesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CapitalizedContractCostAxis=surf_ClinicalMilestonePaymentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CapitalizedContractCostAxis=surf_RegulatoryMilestonePaymentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CapitalizedContractCostAxis=surf_SalesMilestonePaymentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

Name:	us-gaap_CapitalizedContractCostAxis=surf_DevelopmentMilestoneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CapitalizedContractCostAxis=surf_SalesMilestoneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Collaboration and License Agreements - Additional Information (Details)	1 Months Ended	3 Months Ended		12 Months Ended
	Jan. 31, 2016 target	Mar. 31, 2023 USD ($) obligation	Mar. 31, 2022 USD ($)	Dec. 31, 2020 USD ($)	Aug. 31, 2021 USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
License related revenue		$ 0	$ 30,000,000
GSK Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contract with customer, expiration period		10 years
Number of performance obligations \| obligation		3
Transaction price		$ 90,286,000
GSK Agreement \| License
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
License related revenue		0	30,000,000
GSK Agreement \| License \| Transferred at Point in Time
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment					$ 85,000,000
License related revenue				$ 85,000,000
GSK Agreement \| License \| Transferred over Time
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Additional payments to be received		4,524,000			4,314,000
GSK Agreement \| Transition Services \| Transferred over Time
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Additional payments to be received		762,000			$ 950,000
GSK Agreement \| Clinical Milestone Payment
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential milestones payment		60,000,000
GSK Agreement \| Regulatory Milestone Payment
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential milestones payment		155,000,000
GSK Agreement \| Sales Milestone Payment
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential milestones payment		485,000,000
Novartis Collaboration
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of option targets \| target	4
Number of option targets purchased \| target	3
Upfront, milestone, and option purchase payments, aggregate amount		150,000,000
Novartis Collaboration \| Novartis Institutes for Biomedical Research, Inc.
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue		0	$ 0
Novartis Collaboration \| Novartis Institutes for Biomedical Research, Inc. \| Development Milestone
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential milestones payment		325,000,000
Novartis Collaboration \| Novartis Institutes for Biomedical Research, Inc. \| Sales Milestone
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential milestones payment		$ 200,000,000