XML 84 R63.htm IDEA: XBRL DOCUMENT
v3.24.0.1

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2023 | Dec. 31, 2022
Income Taxes [Line Items] |  |
Increase (decrease) in valuation allowance | $ 72,900 | $ 35,900
Valuation allowance for deferred tax assets, description | The Company has provided a valuation allowance for the full amount of the net deferred tax assets as the realization of the deferred tax assets is not determined to be more likely than not. The valuation allowance increased by $72.9 million in 2023 due to the increase in deferred tax assets, primarily driven by the generation of net operating losses and capitalized research expenses, and capitalized start-up costs. The valuation allowance increased by $35.9 million in 2022 due to the increase in deferred tax assets, primarily driven by the generation of net operating losses and capitalized start-up costs, partially offset by a decrease to other deferred tax assets. |
Federal net operating losses | $ 136,400 |
State net operating losses | 63,500 |
Uncertain tax positions | 100 |
Deferred tax asset | 79,600 |
Deferred tax assets, Expenses required to be capitalized | 53,700 |
Internal Revenue Service [Member] |  |
Income Taxes [Line Items] |  |
Interest or penalties recorded during the period | 0 | $ 0
Unrecognized income tax benefits that would affect effective tax rate | $ 0 |
Federal [Member] |  |
Income Taxes [Line Items] |  |
Operating loss carryforward expiration period | 2026 |
Deferred tax assets research credits | $ 8,900 |
Deferred tax assets research credits expiration period | 2024 |
Federal [Member] | Indefinite Carryforward Period [Member] |  |
Income Taxes [Line Items] |  |
Federal net operating losses | $ 114,300 |
State net operating losses | 900 |
Federal [Member] | Begin to Expire in 2026 [Member] |  |
Income Taxes [Line Items] |  |
Federal net operating losses | 22,100 |
State [Member] |  |
Income Taxes [Line Items] |  |
Current State Income Expense | $ 300 |
Operating loss carryforward expiration period | 2026 |
Deferred tax assets research credits | $ 3,800 |
Deferred tax assets research credits expiration period | 2024 |
State [Member] | Begin to Expire in 2026 [Member] |  |
Income Taxes [Line Items] |  |
Federal net operating losses | $ 62,600 |

X
- Definition Deferred tax assets operating loss carryforwards expiration period. + References No definition available. + Details
Name: | sndx_DeferredTaxAssetsOperatingLossCarryforwardsExpirationPeriod
Namespace Prefix: | sndx_
Data Type: | xbrli:gYearItemType
Balance Type: | na
Period Type: | duration

X
- Definition Deferred tax assets research credits expiration period. + References No definition available. + Details
Name: | sndx_DeferredTaxAssetsResearchCreditsExpirationPeriod
Namespace Prefix: | sndx_
Data Type: | xbrli:gYearItemType
Balance Type: | na
Period Type: | duration

X
- Definition Income taxes. + References No definition available. + Details
Name: | sndx_IncomeTaxesLineItems
Namespace Prefix: | sndx_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of current state and local tax expense (benefit) attributable to income (loss) from continuing operations. Includes, but is not limited to, current regional, territorial, and provincial tax expense (benefit) for non-US (United States of America) jurisdiction. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 235 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08(h)(1)(Note 1)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Name Accounting Standards Codification -Section 50 -Paragraph 9 -Subparagraph (a) -SubTopic 10 -Topic 740 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482685/740-10-50-9 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 6.I.7) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479360/740-10-S99-1 + Details
Name: | us-gaap_CurrentStateAndLocalTaxExpenseBenefit
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount, after allocation of valuation allowances and deferred tax liability, of deferred tax asset attributable to deductible differences and carryforwards, without jurisdictional netting. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482685/740-10-50-2 + Details
Name: | us-gaap_DeferredTaxAssetsLiabilitiesNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible domestic operating loss carryforwards. Excludes state and local operating loss carryforwards. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482685/740-10-50-6 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 8 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482685/740-10-50-8 + Details
Name: | us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsDomestic
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible state and local operating loss carryforwards. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482685/740-10-50-6 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 8 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482685/740-10-50-8 + Details
Name: | us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsStateAndLocal
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible research tax credit carryforwards. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482685/740-10-50-6 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 8 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482685/740-10-50-8 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482685/740-10-50-3 + Details
Name: | us-gaap_DeferredTaxAssetsTaxCreditCarryforwardsResearch
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount, before allocation of valuation allowances, of deferred tax asset attributable to deductible differences from reserves and accruals, compensation and benefit costs, and other provisions, reserves, and allowances. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482685/740-10-50-6 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 8 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482685/740-10-50-8 + Details
Name: | us-gaap_DeferredTaxAssetsTaxDeferredExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of expense for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 15 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482685/740-10-50-15 + Details
Name: | us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of increase (decrease) in unrecognized tax benefits attributable to uncertain tax positions taken in tax returns. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 15A -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482685/740-10-50-15A + Details
Name: | us-gaap_UnrecognizedTaxBenefitsPeriodIncreaseDecrease
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | duration

X
- Definition The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 15A -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482685/740-10-50-15A + Details
Name: | us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of increase (decrease) in the valuation allowance for a specified deferred tax asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482685/740-10-50-2 + Details
Name: | us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Describes the methodologies and assumptions on which the valuation allowance is based for deferred tax assets for which it is more likely than not that all or a portion of the deferred tax asset will not be realized. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482685/740-10-50-2 + Details
Name: | us-gaap_ValuationAllowanceMethodologiesAndAssumptions
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_IncomeTaxAuthorityNameAxis=us-gaap_InternalRevenueServiceIRSMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeTaxAuthorityAxis=us-gaap_DomesticCountryMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_TaxPeriodAxis=sndx_IndefiniteCarryforwardPeriodMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_TaxPeriodAxis=sndx_BeginToExpireInTwoThousandAndTwentySixMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeTaxAuthorityAxis=us-gaap_StateAndLocalJurisdictionMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |