XML 72 R53.htm IDEA: XBRL DOCUMENT
v3.22.0.1

LEASES - Narrative (Details) | 12 Months Ended
--- | ---
Dec. 31, 2021 CAD ($) ft² term | Dec. 31, 2021 USD ($) ft² term | Dec. 31, 2020 USD ($)
Lessee, Lease, Description [Line Items] |  |  |
Short term property leases |  | $ 262,000 | $ 261,000
Operating lease cost, including related operating cost |  | $ 327,000 | $ 301,000
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration] | Other assets | Other assets | Other assets
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration] | Other current liabilities | Other current liabilities | Other current liabilities
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List] | Other non-current liabilities | Other non-current liabilities | Other non-current liabilities
Canada |  |  |
Lessee, Lease, Description [Line Items] |  |  |
Office space (in square feet) | ft² | 31,100 | 31,100 |
Lease term | 2 years | 2 years |
Renewal option | term | 1 | 1 |
Renewal term | 3 years | 3 years |
Monthly rent | $ 18,100 | $ 14,300 |
Related operating expenses | $ 18,200 | $ 14,300 |
Massachusetts And Pennsylvania | Minimum |  |  |
Lessee, Lease, Description [Line Items] |  |  |
Renewal term | 3 months | 3 months |
Massachusetts And Pennsylvania | Maximum |  |  |
Lessee, Lease, Description [Line Items] |  |  |
Renewal term | 6 months | 6 months |
Massachusetts |  |  |
Lessee, Lease, Description [Line Items] |  |  |
Monthly rent |  | $ 2,100 |
Pennsylvania |  |  |
Lessee, Lease, Description [Line Items] |  |  |
Monthly rent |  | $ 18,400 |

X
- Definition Lessee Leasing Arrangements, Operating Leases, Number Of Renewal Option + References No definition available. + Details
Name: | sesn_LesseeLeasingArrangementsOperatingLeasesNumberOfRenewalOption
Namespace Prefix: | sesn_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Operating Lease, Monthly Rent + References No definition available. + Details
Name: | sesn_OperatingLeaseMonthlyRent
Namespace Prefix: | sesn_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Operating Lease, Other Monthly Operating Expenses + References No definition available. + Details
Name: | sesn_OperatingLeaseOtherMonthlyOperatingExpenses
Namespace Prefix: | sesn_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Operating Leases Area Of Office Space + References No definition available. + Details
Name: | sesn_OperatingLeasesAreaOfOfficeSpace
Namespace Prefix: | sesn_
Data Type: | dtr-types:areaItemType
Balance Type: | na
Period Type: | duration

X
- 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_LesseeLeaseDescriptionLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Term of lessee's operating lease renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=123408670&loc=SL77918673-209980 + Details
Name: | us-gaap_LesseeOperatingLeaseRenewalTerm
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | instant

X
- Definition Term of lessee's 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/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=123408670&loc=SL77918673-209980 + Details
Name: | us-gaap_LesseeOperatingLeaseTermOfContract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount of single lease cost, calculated by allocation of remaining cost of lease over remaining lease term. Includes, but is not limited to, single lease cost, after impairment of right-of-use asset, calculated by amortization of remaining right-of-use asset and accretion of lease liability. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 55 -Paragraph 53 -URI http://asc.fasb.org/extlink&oid=123414884&loc=SL77918982-209971 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123408670&loc=SL77918686-209980 + Details
Name: | us-gaap_OperatingLeaseCost
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Indicates line item in statement of financial position that includes current operating lease liability. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=123391704&loc=SL77918631-209977 + Details
Name: | us-gaap_OperatingLeaseLiabilityCurrentStatementOfFinancialPositionExtensibleList
Namespace Prefix: | us-gaap_
Data Type: | enum2:enumerationSetItemType
Balance Type: | na
Period Type: | instant

X
- Definition Indicates line item in statement of financial position that includes noncurrent operating lease liability. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=123391704&loc=SL77918631-209977 + Details
Name: | us-gaap_OperatingLeaseLiabilityNoncurrentStatementOfFinancialPositionExtensibleList
Namespace Prefix: | us-gaap_
Data Type: | enum2:enumerationSetItemType
Balance Type: | na
Period Type: | instant

X
- Definition Indicates line item in statement of financial position that includes operating lease right-of-use asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=123391704&loc=SL77918631-209977 + Details
Name: | us-gaap_OperatingLeaseRightOfUseAssetStatementOfFinancialPositionExtensibleList
Namespace Prefix: | us-gaap_
Data Type: | enum2:enumerationSetItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount of short-term lease cost, excluding expense for lease with term of one month or less. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=123408670&loc=SL77918686-209980 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 55 -Paragraph 53 -URI http://asc.fasb.org/extlink&oid=123414884&loc=SL77918982-209971 + Details
Name: | us-gaap_ShortTermLeaseCost
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | srt_StatementGeographicalAxis=country_CA
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_StatementGeographicalAxis=sesn_MassachusettsAndPennsylvaniaMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_StatementGeographicalAxis=stpr_MA
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_StatementGeographicalAxis=stpr_PA
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |