The amount of transaction fees under the agreement.

No definition available.

Name:	nxtc_CollaborationAgreementTransactionPrice
Namespace Prefix:	nxtc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents the maximum amount of development and regulatory milestones and sales milestones payable upon option exercise.

+ References

No definition available.

+ Details

Name:	nxtc_CollaborativeArrangementMaximumDevelopmentRegulatoryAndSalesMilestonePayableUponOptionExercise
Namespace Prefix:	nxtc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the maximum amount of development and regulatory milestones and sales milestones receivable.

+ References

No definition available.

+ Details

Name:	nxtc_CollaborativeArrangementMaximumDevelopmentRegulatoryAndSalesMilestoneReceivable
Namespace Prefix:	nxtc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents the amount of upfront non-refundable payment received under collaborative arrangement.

+ References

No definition available.

+ Details

Name:	nxtc_CollaborativeArrangementUpfrontNonRefundablePaymentReceived
Namespace Prefix:	nxtc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The number of performance obligations.

+ References

No definition available.

+ Details

Name:	nxtc_RevenueRecognitionNumberOfPerformanceObligations
Namespace Prefix:	nxtc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

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

- Definition

Proceeds from issuance of capital stock which provides for a specific dividend that is paid to the shareholders before any dividends to common stockholders and which takes precedence over common stockholders in the event of liquidation.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3255-108585

+ Details

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

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045

+ Details

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

- Details

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

- Details

Name:	srt_CounterpartyNameAxis=nxtc_EliLillyAndCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Agreement with Eli Lilly and Company - Other (Details)			12 Months Ended
Agreement with Eli Lilly and Company - Other (Details)	Dec. 02, 2019 USD ($)	Nov. 02, 2018 USD ($)	Dec. 31, 2019 USD ($) item	Dec. 31, 2018 USD ($)
Collaborative Arrangements
Equity investment	$ 160,900,000			$ 122,223,000
Revenue			$ 6,347,000
Lilly Agreement
Collaborative Arrangements
Upfront non-refundable payment received		$ 25,000,000
Equity investment		15,000,000
The number of performance obligations. \| item			2
Revenue			$ 6,300,000	$ 0
Lilly Agreement \| Lilly
Collaborative Arrangements
Maximum development and regulatory milestones and sales milestone receivable		1,400,000,000
Maximum development and regulatory milestones and sales milestone payable upon option exercise		710,000,000
Transaction price		$ 32,700,000