The amount of transaction fees under the agreement.

No definition available.

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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

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- Definition

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

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

Represents the period of expiry from date of agreement under collaborative arrangement.

+ References

No definition available.

+ Details

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- Definition

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

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The number of performance obligations.

+ References

No definition available.

+ Details

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Data Type:	xbrli:integerItemType
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- 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

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- 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=109223946&loc=d3e3255-108585

+ Details

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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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130543-203045

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130539-203045

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130545-203045

+ Details

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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

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Agreement with Eli Lilly and Company - Other (Details) $ in Thousands		3 Months Ended	9 Months Ended		12 Months Ended
	Nov. 02, 2018 USD ($) item	Sep. 30, 2019 USD ($)	Sep. 30, 2019 USD ($) item	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Collaborative Arrangements
Equity investment	$ 15,000			$ 31,000	$ 122,223	$ 25,000
Revenue		$ 1,583	$ 4,342
Lilly Agreement
Collaborative Arrangements
Period of expiry from date of agreement	4 years
Upfront non-refundable payment received	$ 25,000
Equity investment	$ 15,000
The number of performance obligations. \| item	2		2
Revenue		$ 1,600	$ 4,300		$ 0
Lilly Agreement \| Lilly
Collaborative Arrangements
Maximum development and regulatory milestones and sales milestone receivable	$ 1,400,000
Maximum development and regulatory milestones and sales milestone payable upon option exercise	710,000
Transaction price	$ 32,700