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.

+ Details

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

- Definition

Exercise price per share or per unit of warrants or rights outstanding.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(i)(4))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of securities into which each warrant or right may be converted. For example, but not limited to, each warrant may be converted into two shares.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of warrants or rights outstanding.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(i))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_DebtInstrumentAxis=ntra_SecuredLoanArrangementMember
Namespace Prefix:
Data Type:	na
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Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=ntra_SeriesBConvertiblePreferredStockMember
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Data Type:	na
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- Details

Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_CommonStockMember
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Warrants (Details) - $ / shares	Mar. 31, 2016	Jul. 31, 2015	Dec. 31, 2009
Secured Loan Arrangement
Class of Stock [Line Items]
Warrants outstanding (in shares)	376,691
Warrants exercise price (in dollars per share)	$ 2.3229
B
Class of Stock [Line Items]
Warrants outstanding (in shares)			33,742
Warrants exercise price (in dollars per share)			$ 1.8908
Common stock \| B
Class of Stock [Line Items]
Common stock issued for each warrant (in shares)		1