XML 43 R32.htm IDEA: XBRL DOCUMENT
v3.25.3

Convertible Preferred Stock- Summary of Preferred Stock (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2025 | Jun. 30, 2025 | Mar. 31, 2025 | Sep. 30, 2025
Increase (Decrease) in Temporary Equity [Roll Forward] |  |  |  |
Temporary equity, beginning balance (in shares) |  |  | 175,190,188 | 175,190,188
Temporary equity, beginning balance | $ 126,700 | $ 94,147 | $ 74,475 | $ 74,475
Exercise of preferred stock warrants ( in shares) |  |  |  | 1,988,999
Exercise of preferred stock warrant | 264 | 650 | 130 | $ 455
Issuance of Series E (in shares) |  |  |  | 58,774,312
Issuance of Series E |  | 31,903 | 19,542 | $ 40,130
Conversion of redeemable convertible preferred stock to common stock upon IPO (in shares) |  |  |  | (235,953,499)
Conversion of redeemable convertible preferred stock to common stock upon IPO | $ (126,964) |  |  | $ (115,060)
Temporary equity, ending balance (in shares) | 0 |  |  | 0
Temporary equity, ending balance | $ 0 | $ 126,700 | $ 94,147 | $ 0
Series Seed Convertible Preferred Stock |  |  |  |
Increase (Decrease) in Temporary Equity [Roll Forward] |  |  |  |
Temporary equity, beginning balance (in shares) |  |  | 15,851,401 | 15,851,401
Temporary equity, beginning balance |  |  | $ 1,337 | $ 1,337
Exercise of preferred stock warrants ( in shares) |  |  |  | 988,999
Exercise of preferred stock warrant |  |  |  | $ 83
Conversion of redeemable convertible preferred stock to common stock upon IPO (in shares) |  |  |  | (16,840,400)
Conversion of redeemable convertible preferred stock to common stock upon IPO |  |  |  | $ (1,420)
Temporary equity, ending balance (in shares) | 0 |  |  | 0
Temporary equity, ending balance | $ 0 |  |  | $ 0
Series A Convertible Preferred Stock |  |  |  |
Increase (Decrease) in Temporary Equity [Roll Forward] |  |  |  |
Temporary equity, beginning balance (in shares) |  |  | 22,399,370 | 22,399,370
Temporary equity, beginning balance |  |  | $ 5,600 | $ 5,600
Conversion of redeemable convertible preferred stock to common stock upon IPO (in shares) |  |  |  | (22,399,370)
Conversion of redeemable convertible preferred stock to common stock upon IPO |  |  |  | $ (5,600)
Temporary equity, ending balance (in shares) | 0 |  |  | 0
Temporary equity, ending balance | $ 0 |  |  | $ 0
Series B Convertible Preferred Stock |  |  |  |
Increase (Decrease) in Temporary Equity [Roll Forward] |  |  |  |
Temporary equity, beginning balance (in shares) |  |  | 5,913,964 | 5,913,964
Temporary equity, beginning balance |  |  | $ 2,200 | $ 2,200
Exercise of preferred stock warrants ( in shares) |  |  |  | 1,000,000
Exercise of preferred stock warrant |  |  |  | $ 372
Conversion of redeemable convertible preferred stock to common stock upon IPO (in shares) |  |  |  | (6,913,964)
Conversion of redeemable convertible preferred stock to common stock upon IPO |  |  |  | $ (2,572)
Temporary equity, ending balance (in shares) | 0 |  |  | 0
Temporary equity, ending balance | $ 0 |  |  | $ 0
Series C Convertible Preferred Stock |  |  |  |
Increase (Decrease) in Temporary Equity [Roll Forward] |  |  |  |
Temporary equity, beginning balance (in shares) |  |  | 50,116,284 | 50,116,284
Temporary equity, beginning balance |  |  | $ 21,550 | $ 21,550
Conversion of redeemable convertible preferred stock to common stock upon IPO (in shares) |  |  |  | (50,116,284)
Conversion of redeemable convertible preferred stock to common stock upon IPO |  |  |  | $ (21,550)
Temporary equity, ending balance (in shares) | 0 |  |  | 0
Temporary equity, ending balance | $ 0 |  |  | $ 0
Series D Convertible Preferred Stock |  |  |  |
Increase (Decrease) in Temporary Equity [Roll Forward] |  |  |  |
Temporary equity, beginning balance (in shares) |  |  | 80,909,169 | 80,909,169
Temporary equity, beginning balance |  |  | $ 43,788 | $ 43,788
Conversion of redeemable convertible preferred stock to common stock upon IPO (in shares) |  |  |  | (80,909,169)
Conversion of redeemable convertible preferred stock to common stock upon IPO |  |  |  | $ (43,788)
Temporary equity, ending balance (in shares) | 0 |  |  | 0
Temporary equity, ending balance | $ 0 |  |  | $ 0
Series E Convertible Preferred Stock |  |  |  |
Increase (Decrease) in Temporary Equity [Roll Forward] |  |  |  |
Temporary equity, beginning balance (in shares) |  |  | 0 | 0
Temporary equity, beginning balance |  |  | $ 0 | $ 0
Issuance of Series E (in shares) |  |  |  | 58,774,312
Issuance of Series E |  |  |  | $ 40,130
Conversion of redeemable convertible preferred stock to common stock upon IPO (in shares) |  |  |  | (58,774,312)
Conversion of redeemable convertible preferred stock to common stock upon IPO |  |  |  | $ (40,130)
Temporary equity, ending balance (in shares) | 0 |  |  | 0
Temporary equity, ending balance | $ 0 |  |  | $ 0

X
- Definition Temporary Equity, Shares, Conversion of Convertible Securities + References No definition available. + Details
Name: | si_TemporaryEquitySharesConversionOfConvertibleSecurities
Namespace Prefix: | si_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Temporary Equity, Stock Issued During Period, Share, Warrants Exercised + References No definition available. + Details
Name: | si_TemporaryEquityStockIssuedDuringPeriodShareWarrantsExercised
Namespace Prefix: | si_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Temporary Equity, Stock Issued During Period, Shares, New Issues + References No definition available. + Details
Name: | si_TemporaryEquityStockIssuedDuringPeriodSharesNewIssues
Namespace Prefix: | si_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Temporary Equity, Stock Issued During Period, Value, Warrants Exercised + References No definition available. + Details
Name: | si_TemporaryEquityStockIssuedDuringPeriodValueWarrantsExercised
Namespace Prefix: | si_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Temporary Equity, Value, Conversion of Convertible Securities + References No definition available. + Details
Name: | si_TemporaryEquityValueConversionOfConvertibleSecurities
Namespace Prefix: | si_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
Name: | us-gaap_IncreaseDecreaseInTemporaryEquityRollForward
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Carrying amount, attributable to parent, of an entity's issued and outstanding stock which is not included within permanent equity. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. Includes stock with a put option held by an ESOP and stock redeemable by a holder only in the event of a change in control of the issuer. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 718 -SubTopic 30 -Name Accounting Standards Codification -Section S55 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479772/718-30-S55-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 480 -SubTopic 10 -Name Accounting Standards Codification -Section S50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479857/480-10-S50-1 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 480 -SubTopic 10 -Name Accounting Standards Codification -Section S45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479887/480-10-S45-1 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 480 -SubTopic 10 -Name Accounting Standards Codification -Section S45 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479887/480-10-S45-2 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 480 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (01)(i) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480244/480-10-S99-1 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(23)(a)(1)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 14.E.Q2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479830/718-10-S99-1 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1A -Subparagraph (SX 210.13-01(a)(4)(i)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A Reference 9: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1A -Subparagraph (SX 210.13-01(a)(4)(iv)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A Reference 10: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1A -Subparagraph (SX 210.13-01(a)(5)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A Reference 11: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1B -Subparagraph (SX 210.13-02(a)(4)(i)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B Reference 12: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1B -Subparagraph (SX 210.13-02(a)(4)(iv)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B Reference 13: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1B -Subparagraph (SX 210.13-02(a)(5)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B + Details
Name: | us-gaap_TemporaryEquityCarryingAmountAttributableToParent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The number of securities classified as temporary equity that have been issued and are held by the entity's shareholders. Securities outstanding equals securities issued minus securities held in treasury. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. If convertible, the issuer does not control the actions or events necessary to issue the maximum number of shares that could be required to be delivered under the conversion option if the holder exercises the option to convert the stock to another class of equity. If the security is a warrant or a rights issue, the warrant or rights issue is considered to be temporary equity if the issuer cannot demonstrate that it would be able to deliver upon the exercise of the option by the holder in all cases. Includes stock with put option held by ESOP and stock redeemable by holder only in the event of a change in control of the issuer. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 480 -SubTopic 10 -Name Accounting Standards Codification -Section S50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479857/480-10-S50-1 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(27)(b)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 + Details
Name: | us-gaap_TemporaryEquitySharesOutstanding
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Value of new stock classified as temporary equity issued during the period. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 480 -SubTopic 10 -Name Accounting Standards Codification -Section S50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479857/480-10-S50-2 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 480 -SubTopic 10 -Name Accounting Standards Codification -Section S45 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479887/480-10-S45-2 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 480 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (04) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480244/480-10-S99-1 Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 480 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (01) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480244/480-10-S99-1 + Details
Name: | us-gaap_TemporaryEquityStockIssuedDuringPeriodValueNewIssues
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=si_SeedConvertiblePreferredStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=us-gaap_SeriesAPreferredStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=us-gaap_SeriesBPreferredStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=us-gaap_SeriesCPreferredStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=us-gaap_SeriesDPreferredStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=us-gaap_SeriesEPreferredStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |