Settlement agreement amount plus applicable interest to be paid in installments.

No definition available.

Name:	ntra_LitigationSettlementAmountPlusInterestToBePaidInInstallments
Namespace Prefix:	ntra_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The number of equal quarterly installment payments under settlement agreement.

+ References

No definition available.

+ Details

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Namespace Prefix:	ntra_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Aggregate carrying amount of the estimated litigation liability for known or estimated probable loss from litigation, which may include attorneys' fees and other litigation costs.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.25)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

Amount of damages paid to the plaintiff in the legal matter.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14557-108349

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14435-108349

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349

+ Details

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

- Definition

Reflects the estimated amount of loss from the specified contingency as of the balance sheet date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14435-108349

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 9
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14557-108349

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=115931803&loc=d3e12021-110248

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

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

- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3536-108585

+ Details

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

- Definition

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

+ References

No definition available.

+ Details

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

- Details

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Namespace Prefix:
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- Details

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Data Type:	na
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- Details

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

- Details

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

- Details

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Data Type:	na
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Period Type:

- Details

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Data Type:	na
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- Details

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Data Type:	na
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- Details

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Data Type:	na
Balance Type:
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- Details

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Data Type:	na
Balance Type:
Period Type:

- Details

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Data Type:	na
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- Details

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Data Type:	na
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Commitments and Contingencies (Details) $ in Millions		1 Months Ended	12 Months Ended
Commitments and Contingencies (Details) $ in Millions	Mar. 07, 2018 USD ($) installment	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2017 USD ($)
Other commitments
Accrued settlement liability	$ 11.4		$ 1.4		$ 11.4
Settlement agreement, amount plus applicable interest to be paid in installments	$ 5.3
Settlement agreement, number of equal quarterly installments \| installment	4
Settlement amount		$ 1.4	5.3
Settlement agreement installment paid		$ 1.4	$ 10.3
Inventory material
Other commitments
Purchase commitment				$ 5.8
Gene sequencing data analysis commitment
Other commitments
Purchase commitment				1.3
Another supplier \| Inventory material
Other commitments
Purchase commitment				4.4
Supplier three \| Biological sample processing and storage
Other commitments
Purchase commitment				0.3
Supplier Four \| Diagnostic reagents
Other commitments
Purchase commitment				0.4
Supplier Five \| Tests
Other commitments
Purchase commitment				2.6
Supplier Six
Other commitments
Purchase commitment				1.4
Securities related claims
Other commitments
Estimate of possible loss				1.5
Commercial general liability claims
Other commitments
Estimate of possible loss				$ 0.3