Name:	ntra_AgreementTerm
Namespace Prefix:	ntra_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

The total amount of the contingent obligation under letters of credit that expired.

No definition available.

Name:	ntra_LettersOfCreditExpired
Namespace Prefix:	ntra_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The amount of cash paid for the settlement of litigation or for other legal issues during the period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3536-108585

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

Minimum amount of purchase arrangement in which the entity has agreed to expend funds to procure goods or services from a supplier.

No definition available.

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

Amount of transaction price allocated to performance obligation that has not been recognized as revenue.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 270
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=84173487&loc=SL51747714-108306

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=82913847&loc=SL49130556-203045

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

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

No definition available.

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

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_ProductOrServiceAxis=ntra_GeneticTestingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_ShareBasedGoodsAndNonemployeeServicesTransactionBySupplierAxis=ntra_SupplierOtherMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_CounterpartyNameAxis=ntra_BeijingGenomicsInstituteMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_ProductOrServiceAxis=ntra_LicenseFeeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: