Accretion of Common Stock to Redemption Value

No definition available.

Name:	kvsb_AccretionOfCommonStockToRedemptionValue
Namespace Prefix:	kvsb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Common stock measured at redemption amount due to initial carrying amount of common stock is less price per share.

+ References

No definition available.

+ Details

Name:	kvsb_CommonStockMeasuredAtRedemptionAmountDueToInitialCarryingAmountOfCommonStockIsLessPricePerShare
Namespace Prefix:	kvsb_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of decrease in additional paid in capital (APIC) resulting from direct costs associated with issuing stock. Includes, but is not limited to, legal and accounting fees and direct costs associated with stock issues under a shelf registration.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=123467817&loc=d3e21463-112644

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770

+ Details

Name:	us-gaap_AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Excludes cash and cash equivalents within disposal group and discontinued operation.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 210
-Section 45
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=118262064&loc=SL116631418-115840

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 852
-SubTopic 10
-Section 55
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=84165509&loc=d3e56426-112766

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.1)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 210
-Section 45
-Paragraph 21
-URI http://asc.fasb.org/extlink&oid=118262064&loc=SL116631419-115840

+ Details

Name:	us-gaap_Cash
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.1)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_CashEquivalentsAtCarryingValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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_ClassOfStockLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Description of credit risk that arises from having significant balances in excess of the Federal Deposit Insurance Corporation or other insurance limits on deposits in financial institutions.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=123594938&loc=d3e13531-108611

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 21
-URI http://asc.fasb.org/extlink&oid=123594938&loc=d3e13537-108611

+ Details

Name:	us-gaap_ConcentrationRiskCreditRiskUninsuredDeposits
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Price of the entity's common stock which would be required to be attained for the conversion feature embedded in the debt instrument to become effective.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentConvertibleStockPriceTrigger
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of net income or loss for the period per each share in instances when basic and diluted earnings per share are the same amount and reported as a single line item on the face of the financial statements. Basic earnings per share is the amount of net income or loss for the period per each share of common stock or unit outstanding during the reporting period. Diluted earnings per share includes the amount of net income or loss for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=125511455&loc=d3e1337-109256

+ Details

Name:	us-gaap_EarningsPerShareBasicAndDiluted
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Value of accretion of temporary equity to its redemption value during the period.

+ References

No definition available.

+ Details

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

- Definition

Amount to be paid per share that is classified as temporary equity by entity upon redemption. 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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 480
-SubTopic 10
-Section S99
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=122040564&loc=d3e177068-122764

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (27)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_TemporaryEquityRedemptionPricePerShare
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- 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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(27)(b))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_TemporaryEquitySharesOutstanding
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of unrecognized tax benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 45
-Paragraph 10B
-URI http://asc.fasb.org/extlink&oid=123427490&loc=SL37586934-109318

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121826272&loc=SL6600010-109319

+ Details

Name:	us-gaap_UnrecognizedTaxBenefits
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount accrued 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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32718-109319

+ Details

Name:	us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	dei_LegalEntityAxis=kvsb_KhoslaVenturesAcquisitionCoIIMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RestatementAxis=srt_ScenarioPreviouslyReportedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RestatementAxis=srt_RestatementAdjustmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementEquityComponentsAxis=kvsb_CommonStockSubjectToPossibleRedemptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_AdditionalPaidInCapitalMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_RetainedEarningsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=us-gaap_CommonClassAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementEquityComponentsAxis=kvsb_NonRedeemableCommonStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=us-gaap_CommonClassBMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=kvsb_TriggeringEventsStockTradingPriceOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=kvsb_TriggeringEventsStockTradingPriceTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=kvsb_TriggeringEventsStockTradingPriceThreeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	2 Months Ended	3 Months Ended		5 Months Ended	8 Months Ended	12 Months Ended
	Mar. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Jun. 30, 2021	Sep. 30, 2021	Dec. 31, 2019	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2018
Class of Stock [Line Items]
Common stock subject to possible redemption (in shares)		61,332,000	61,332,000	61,332,000	61,332,000	61,332,000	61,332,000	61,332,000	61,332,000	52,993,000
Stock issuance costs						$ 196,000
Unrecognized tax benefits						6,972,000	$ 10,144,000			$ 4,647,000
Unrecognised tax benefits penalties and interest accrued						$ 0	$ 0
Khosla
Class of Stock [Line Items]
Cash		$ 572,360	$ 978,280	$ 978,280	$ 572,360
Cash equivalents		$ 0	0	0	$ 0
Common stock subject to possible redemption (in shares)		41,634,412			41,634,412
Shares measured to their redemption amount due to initial carrying amount of the common stock is less price per share (in USD per share)		$ 10.00			$ 10.00
Common stock subject to possible redemption, redemption price per share (in USD per share)		$ 10.00			$ 10.00
Accretion of Class A Common Stock to redemption value	$ (23,576,984)	$ (10,640)		23,576,984	$ 23,587,624
Concentration risk, credit risk, uninsured deposits					250,000
Stock issuance costs				23,576,984	$ 23,576,984
Unrecognized tax benefits		0			0
Unrecognised tax benefits penalties and interest accrued		0			0
Accretion of temporary equity to redemption value		0		2,498,065	0
Khosla \| As Previously Reported
Class of Stock [Line Items]
Accretion of temporary equity to redemption value			2,498,065	2,498,065
Khosla \| Adjustments
Class of Stock [Line Items]
Accretion of temporary equity to redemption value			$ 0	$ 0
Khosla \| Common Stock Subject To Possible Redemption
Class of Stock [Line Items]
Accretion of Class A Common Stock to redemption value	23,576,984
Basic and diluted net income (loss) per share (in USD per share)				$ (0.51)
Khosla \| Additional Paid-in Capital
Class of Stock [Line Items]
Accretion of Class A Common Stock to redemption value	(11,338,767)				11,338,767
Khosla \| Accumulated Deficit
Class of Stock [Line Items]
Accretion of Class A Common Stock to redemption value	$ (12,238,217)	$ (10,640)			$ 12,248,857
Khosla \| Class A Common Stock
Class of Stock [Line Items]
Common stock subject to possible redemption (in shares)		41,634,412	41,634,412	41,634,412	41,634,412
Common stock subject to possible redemption, redemption price per share (in USD per share)			$ 10.00	$ 10.00
Accretion of temporary equity to redemption value		$ 0		$ 0	$ 0
Basic and diluted net income (loss) per share (in USD per share)		$ 0.08		$ (0.60)	$ (0.34)
Khosla \| Class A Common Stock \| Common Stock Subject To Possible Redemption
Class of Stock [Line Items]
Accretion of temporary equity to redemption value		$ 0		$ 2,498,065
Basic and diluted net income (loss) per share (in USD per share)		$ 0.08			$ (0.34)
Khosla \| Class A Common Stock \| Common Stock Subject To Possible Redemption \| As Previously Reported
Class of Stock [Line Items]
Basic and diluted net income (loss) per share (in USD per share)			0.06	$ 0.51
Khosla \| Class A Common Stock \| Common Stock Subject To Possible Redemption \| Adjustments
Class of Stock [Line Items]
Basic and diluted net income (loss) per share (in USD per share)			0.07	0.53
Khosla \| Class A Common Stock \| Non Redeemable Common Stock \| As Previously Reported
Class of Stock [Line Items]
Basic and diluted net income (loss) per share (in USD per share)			0.12	0.60
Khosla \| Class A Common Stock \| Non Redeemable Common Stock \| Adjustments
Class of Stock [Line Items]
Basic and diluted net income (loss) per share (in USD per share)			0.07	$ 0.53
Khosla \| Class B Common Stock
Class of Stock [Line Items]
Accretion of temporary equity to redemption value		$ 0		$ 0	$ 0
Basic and diluted net income (loss) per share (in USD per share)		$ 0.08		$ (0.60)	$ (0.34)
Khosla \| Class B Common Stock \| As Previously Reported
Class of Stock [Line Items]
Basic and diluted net income (loss) per share (in USD per share)			0.12	0.60
Khosla \| Class B Common Stock \| Adjustments
Class of Stock [Line Items]
Basic and diluted net income (loss) per share (in USD per share)			$ 0.07	$ 0.53
Khosla \| Triggering Events Stock Trading Price One \| Class A Common Stock
Class of Stock [Line Items]
Conversion of share, price per share (in USD per share)	$ 20.00				20.00
Khosla \| Triggering Events Stock Trading Price Two \| Class A Common Stock
Class of Stock [Line Items]
Conversion of share, price per share (in USD per share)	25.00				25.00
Khosla \| Triggering Events Stock Trading Price Three \| Class A Common Stock
Class of Stock [Line Items]
Conversion of share, price per share (in USD per share)	$ 30.00				$ 30.00