v3.6.0.2

Fair Value Measurements - Assumptions (Details) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2016 USD ($) company | Dec. 31, 2015 company
Fair Value Inputs, Liabilities, Quantitative Information [Line Items] |  |
Volatility, basket of companies | company | 4 | 15
Warrants |  |
Fair Value Inputs, Liabilities, Quantitative Information [Line Items] |  |
Warrants | $ 3,792 |
Volatility (as a percent) | 61.30% |
Warrant valuation increase | $ 100 |

X
- Definition Represents increase in the warrant valuation resulting from change in the volatility assumption. + References No definition available. + Details
Name: | ntra_ClassOfWarrantOrRightWarrantValuationIncrease
Namespace Prefix: | ntra_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Represents the number of companies considered from a basket comparison in regards to the volatility assumption. + References No definition available. + Details
Name: | ntra_VolatilityAssumptionBasketComparisonNumberOfCompanies
Namespace Prefix: | ntra_
Data Type: | xbrli:positiveIntegerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Measure of dispersion, in percentage terms (for instance, the standard deviation or variance), for a given stock price. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (bbb) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueAssumptionsExpectedVolatilityRate
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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

X
- Definition Fair value portion of warrants not settleable in cash classified as equity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 + Details
Name: | us-gaap_WarrantsNotSettleableInCashFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_ShareholdersEquityClassAxis=us-gaap_WarrantsNotSettleableInCashMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |