Commitments and Contingencies - Additional Information (Details) - USD ($)	3 Months Ended
Mar. 31, 2022	Dec. 31, 2021
Loss Contingencies [Line Items]
Liabilities recorded for agreements	$ 0	$ 0
Agreement with Financial Institution
Loss Contingencies [Line Items]
Letters of credit outstanding amount	$ 2,100,000
Agreement with Financial Institution \| Minimum [Member]
Loss Contingencies [Line Items]
Letter of credit notice period by financial institution before annual expiration date	30 days
Agreement with Financial Institution \| Maximum
Loss Contingencies [Line Items]
Letter of credit notice period by financial institution before annual expiration date	60 days

Letter of credit notice period by financial institution before annual expiration date.

No definition available.

Name:	nktx_LetterOfCreditNoticePeriodByFinancialInstitutionBeforeAnnualExpirationDate
Namespace Prefix:	nktx_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=124440162&loc=d3e12069-110248

+ Details

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

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

Name:	us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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_LossContingenciesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

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

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: