Name:	ntra_AssetAcquisitionConsiderationTransferred
Namespace Prefix:	ntra_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Number of additional shares potentially issuable as consideration upon achievement of milestones in asset acquisition.

No definition available.

Name:	ntra_AssetAcquisitionConsiderationTransferredAdditionalSharesIssuedAndIssuableUponAchievementOfMilestone
Namespace Prefix:	ntra_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

Amount of acquirer's equity interest issued and issuable as part of consideration transferred in asset acquisition.

No definition available.

Name:	ntra_AssetAcquisitionConsiderationTransferredEquityInterestIssuedAndIssuable
Namespace Prefix:	ntra_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of liabilities incurred by the acquirer as part of consideration transferred in asset acquisition.

No definition available.

Name:	ntra_AssetAcquisitionConsiderationTransferredLiabilitiesIncurred
Namespace Prefix:	ntra_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Number of shares issued and issuable as consideration in asset acquisition.

No definition available.

Name:	ntra_AssetAcquisitionConsiderationTransferredSharesIssuedAndIssuable
Namespace Prefix:	ntra_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

Amount of transaction cost incurred as part of consideration transferred in asset acquisition.

No definition available.

Name:	ntra_AssetAcquisitionConsiderationTransferredTransactionCost
Namespace Prefix:	ntra_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

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.

No definition available.

Name:	ntra_AssetAcquisitionLineItems
Namespace Prefix:	ntra_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

The cash outflow for purchases of and capital improvements on property, plant and equipment (capital expenditures), software, and other intangible assets.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3213-108585