Balance Sheet Components - Other Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024	Sep. 30, 2024	Dec. 31, 2023
Balance Sheet Components
Reserves for refunds to insurance carriers	$ 10,113	$ 11,276	$ 15,778	$ 23,245
Accrued charges for third-party testing	13,590	12,321
Testing and laboratory materials from suppliers	13,345	7,893
Marketing and corporate affairs	22,298	16,548
Legal, audit and consulting fees	83,687	54,208
Accrued for acquisition of intangible assets	17,500
Accrued shipping charges	930	1,625
Sales and income tax payable	7,158	4,416
Accrued third-party service fees	9,833	9,046
Clinical trials and studies	15,072	10,097
Operating lease liabilities, current portion	14,006	10,168
Property and equipment purchases	6,313	7,098
Other accrued expenses	2,106	2,197
Total other accrued liabilities	$ 215,951	$ 146,893

Carrying value as of the balance sheet date of acquired intangible assets.

No definition available.

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- Definition

Carrying value as of the balance sheet date of obligations incurred through that date and payable for outsourced testing.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Carrying value as of the balance sheet date of obligations incurred through that date and payable for clinical trials and studies.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Carrying value as of the balance sheet date of obligations incurred and payable for fixed assets.

+ References

No definition available.

+ Details

Name:	ntra_AccruedFixedAssetPurchases
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Carrying value as of the balance sheet date of obligations incurred through that date and payable for shipping charges.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Carrying value as of the balance sheet date of obligations incurred through that date and payable for specimen service fees.

+ References

No definition available.

+ Details

Name:	ntra_AccruedSpecimenServiceFees
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Carrying value as of the balance sheet date of obligations incurred through that date and payable for testing and laboratory materials from suppliers.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of expenses not otherwise itemized or categorized in the footnotes to the financial statements that have been incurred but not yet paid, due within one year or the normal operating cycle, if longer.

+ References

No definition available.

+ Details

Name:	ntra_OtherAccruedSundryExpensesCurrent
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Carrying value as of the balance sheet date of obligations incurred through that date and payable to insurance entities to mitigate potential loss from various risks or to satisfy a promise to provide certain coverage's to employees.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(20))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(24))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(15)(5))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Carrying value as of the balance sheet date of obligations incurred through that date and payable for the marketing, trade and selling of the entity's goods and services. Marketing costs would include expenditures for planning and executing the conception, pricing, promotion, and distribution of ideas, goods, and services; costs of public relations and corporate promotions; and obligations incurred and payable for sales discounts, rebates, price protection programs, etc. offered to customers and under government programs. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Carrying value as of the balance sheet date of obligations incurred through that date and payable for professional fees, such as for legal and accounting services received.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(15)(5))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1

+ Details

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

- References

No definition available.

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Present value of lessee's discounted obligation for lease payments from operating lease, classified as current.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479041/842-20-45-1

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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- Definition

Amount of liabilities classified as other, due within one year or the normal operating cycle, if longer.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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- Definition

Carrying value as of the balance sheet date of liabilities incurred through that date and payable for statutory sales and use taxes, including value added tax.

+ References

+ Details

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Period Type:	instant