Summary of Significant Accounting Policies (Policies)	6 Months Ended
Summary of Significant Accounting Policies (Policies)	Jun. 30, 2015
Summary of Significant Accounting Policies
Basis of Presentation	Basis of Presentation The accompanying unaudited interim condensed consolidated financial statements have been prepared in conformity with U.S. generally accepted accounting principles (“U.S. GAAP”) for interim financial information. In the opinion of management, the unaudited interim condensed consolidated financial information includes only adjustments of a normal recurring nature necessary for a fair presentation of the results of operations, financial position, changes in stockholders’ deficit, and cash flows. The results of operations for the three and six months ended June 30, 2015, are not necessarily indicative of the results for the full year or the results for any future periods. The condensed consolidated balance sheet as of December 31, 2014 has been derived from audited financial statements at that date, these financial statements should be read in conjunction with the audited financial statements, and related notes for the year ended December 31, 2014 included in the prospectus dated July 1, 2015 that forms a part of the Company’s Registration Statement on Form S-1, filed with the SEC pursuant to Rule 424 promulgated under the Securities Act of 1933, as amended.
Principles of Consolidation	Principles of Consolidation The accompanying condensed consolidated financial statements include all the accounts of the Company and its subsidiary. The Company established a subsidiary that operates in the state of Texas in December 2014 to support the Company’s laboratory and operational functions, which became active in the second quarter of 2015. All intercompany balances and transactions have been eliminated.
Use of Estimates	Use of Estimates The preparation of financial statements in accordance with U.S. GAAP requires management to make estimates and assumptions about future events that affect the amounts of assets and liabilities reported, disclosures about contingent assets and liabilities, and reported amounts of revenues and expenses. Significant items subject to such estimates include the allowance for doubtful accounts, stock-based compensation, the fair value of common stock and fair value of debt accounted for under ASC 815, as well as income tax uncertainties. These estimates and assumptions are based on management's best estimates and judgment. Management regularly evaluates its estimates and assumptions using historical experience and other factors; however, actual results could differ from these estimates and could have an adverse effect on the Company's financial statements.
Fair Value	Fair Value The Company discloses the fair value of financial instruments for financial assets and liabilities for which the value is practicable to estimate. Fair value is defined as the price that would be received upon the sale of an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date (exit price). The Company carried senior secured term loan and warrants at fair value according to the fair value measurement guidance.
Risk and Uncertainties	Risk and Uncertainties Financial instruments that potentially subject the Company to credit risk consist of cash and accounts receivable. The Company limits its exposure to credit loss by placing its cash in financial institutions with high credit ratings. The Company's cash may consist of deposits held with banks that may at times exceed federally insured limits. The Company performs evaluations of the relative credit standing of these financial institutions and limits the amount of credit exposure with any one institution. The Company bills third-party payers for certain tests performed. The amount that is ultimately received from the payer for our claim and the timing of such payments are subject to the determination of the payer based on the nature of the test performed and their view of our business practices with respect to collections of plan deductibles and co-payments from patients and other activities. This determination can impact both the amount and timing of when our invoices are collected. Payers may also withhold payments and request refunds of prior payments if we do not perform in accordance with the policies of these payers. The Company performs evaluations of financial conditions for clinics and laboratory partners and generally does not require collateral to support credit sales. Sales to Quest, Progenity, and BioReference Laboratory, Inc. represented 14%, 11%, and 8% of total revenue for the three months ended June 30, 2014 and 15%, 12%, and 8% of total revenue for the six months ended June 30, 2014, respectively. For the three months and six months ended June 30, 2015, there were no customers exceeding 10% of total revenue on an individual basis. As of June 30, 2015, one customer had a receivable balance of approximately 11% of net accounts receivable, and as of December 31, 2014 there were no customers who had a balance greater than 10%.
Revenue Recognition	Revenue Recognition The Company generally bills an insurance carrier, a clinic or a patient for the test upon delivery of the test result. The Company also bills patients directly for out-of-pocket costs not covered by their insurance carriers representing co-pays and deductibles in accordance with their insurance carrier and health plans. Natera may not get reimbursed for tests completed if the tests are not covered under the insurance carrier’s reimbursement policies or Natera is not a qualified provider to the insurance carrier. For tests performed, where an agreed upon reimbursement rate or fixed fee and a predictable history or likelihood of collections exists, the Company recognizes revenues upon delivery of the test report to the prescribing physician based on the established billing rate less contractual and other adjustments, such as an allowance for doubtful accounts, to arrive at the amount that the Company expects to collect. In all other situations, as the Company does not have a sufficient history of collection and is not able to determine collectability, the Company recognizes revenues when cash is received. From time to time, we receive requests for refunds of payments previously made by insurance carriers. The Company has established an accrued liability for potential refund requests based on our experience. In cases where the Company sells its tests through its laboratory partners, the majority of the laboratory partners bill the patient, clinic, or insurance carrier for the performance of the Company's tests. For tests sold through a limited number of its laboratory partners, the Company bills directly to a patient, clinic or insurance carrier, or a combination of the insurance carrier and patient for the fees. The Company considers its services rendered when it delivers reports of its test results to the laboratory partner, clinic or patient. When the Company has contracted fixed rates for its services and collectability of its revenues is reasonably assured, it recognizes revenues upon delivery of test reports. The fixed fees identified in contracts with laboratory partners change only if a pricing amendment is agreed upon between both parties. For cases in which there is no fixed price established with a laboratory partner, the Company then recognizes revenues from partner distributed tests on a cash basis. Certain of the Company's arrangements include multiple deliverables. For revenue arrangements with multiple deliverables, the Company evaluates each deliverable to determine whether it qualifies as a separate unit of accounting. This determination is based on whether the deliverable has "stand-alone value" to the customer and whether a general right of return exists. The consideration that is fixed or determinable is then allocated to each separate unit of accounting based on the relative selling price of each deliverable. The consideration allocated to each unit of accounting is recognized as the related goods or services are delivered, limited to the consideration that is not contingent upon future deliverables. The Company uses judgment in identifying the deliverables in its arrangements, assessing whether each deliverable is a separate unit of accounting, and in determining the best estimate of selling price for certain deliverables. The Company also uses judgment in determining the period over which the deliverables are recognized in certain of its arrangements. Any amounts received that do not meet the criteria for revenue recognition are recorded as deferred revenue until such criteria are met. The Company receives royalty revenue through the licensing and the provisioning of services to support the use of the Company's proprietary technology with its customer. Royalty revenues are recognized when earned under the terms of the related agreements and are included in Other Revenues in the statements of operations.
Stock Based Compensation	Stock‑Based Compensation Stock‑based compensation related to stock options granted to the Company’s employees is measured at the grant date based on the fair value of the award. The fair value is recognized as expense over the requisite service period, which is generally the vesting period of the respective awards. No compensation cost is recognized on stock options for employees who do not render the requisite service and therefore forfeit their rights to the stock options. The Company uses the Black‑Scholes option‑pricing model to estimate the fair value of its stock options. The Company accounts for stock options issued to non-employees based on the estimated fair value of the awards using the Black-Scholes option-pricing model. The measurement of stock-based compensation is subject to periodic adjustments as the underlying equity instruments vest, and the resulting change in value, if any, is recognized in the Company's statements of operations during the period that the related services are rendered. The Black-Scholes option-pricing model requires the input of the Company's expected stock price volatility, the expected life of the awards, a risk-free interest rate, and expected dividends. Determining these assumptions requires significant judgment. The expected term was based on the simplified method and where the Company did not qualify to use the simplified method, the Company used the lattice model, and the volatility rate was based on that of publicly traded companies in the DNA sequencing, diagnostics, or personalized medicine industries. When selecting the public companies in these industries to be used in the volatility calculation, companies were selected with comparable characteristics to the Company, including enterprise value and financial leverage. Companies were also selected with historical share price volatility sufficient to meet the expected life of the Company's stock options. The historical volatility data was computed using the daily closing prices for the selected companies' shares during the equivalent period of the calculated expected term of the Company's stock options. The expected life of the non-employee option grants was based on their remaining contractual life at the measurement date. The risk-free interest rate assumption was based on U.S. Treasury instruments with maturities that were consistent with the option's expected life. The expected dividend assumption was based on the Company's history and expectation of dividend payouts.
Warrants	Warrants The Company accounts for warrants to purchase shares of its common stock and convertible preferred stock as a liability at fair value on the balance sheet date because the Company may be obligated to redeem these warrants at some point in the future. The warrants are subject to remeasurement at each balance sheet date, with changes in fair value recognized as a gain or loss from the changes in fair value of the warrants in the statements of operations. The Company will continue to adjust the liability for changes in fair value until such time that the warrants are converted or expire.
Other Comprehensive Income (Loss)	Other Comprehensive Income (Loss) Net loss and other comprehensive loss are the same because the Company had no unrealized gains or losses or other items for inclusion in other comprehensive loss.
Net Loss per Share	Net Loss per Share Basic net loss per share is calculated by dividing net loss by the weighted-average shares outstanding during the period, without consideration for potential dilutive shares. Diluted net loss per share is calculated by adjusting the weighted-average shares outstanding for the dilutive effect of potential dilutive shares outstanding for the period, determined using the if-converted method. For purposes of the diluted net loss per share calculation, convertible preferred stock, stock options, convertible notes, unvested shares subject to repurchase, and warrants are considered potential dilutive shares but are excluded from the calculation of diluted net loss per share because their effect would be anti-dilutive. Therefore, basic and diluted net loss per share was the same for all periods presented.
Property and Equipment	Property and Equipment Property and equipment, including purchased and internally developed software, are stated at cost. Depreciation is calculated using the straight-line method over the estimated useful lives of the assets, which are generally three years. Leasehold improvements are amortized using the straight-line method over the estimated useful lives of the assets or the remaining term of the lease, whichever is shorter. The Company periodically review the depreciable lives assigned to property and equipment placed in service and change the estimates of useful lives to reflect the results of such reviews. During the three months ended June 30, 2015, the Company increased the depreciable lives of certain sequencing and automation machinery equipment from three years to five years. The effect of this change in estimate for each of the three and six months ended June 30, 2015 was a decrease in loss from operations and net loss of $0.6 million. The effect of this change in estimate was a decrease in net basic and diluted loss per share of $0.11 for the three months ended June 30, 2015 and $0.12 for the six months ended June 30, 2015.
Recent Accounting Pronouncements	Recent Accounting Pronouncements From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed below, the Company believes that the impact of recently issued standards that are not yet effective will not have a material impact on its financial position or results of operations upon adoption. In August 2014, the Financial Accounting Standards Board issued Accounting Standards Update No. 2014‑15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern (ASU 2014‑15). ASU 2014‑15 requires management to evaluate whether there is substantial doubt about an entity’s ability to continue as a going concern and to provide related footnote disclosures. In doing so, companies will have reduced diversity in the timing and content of footnote disclosures compared to footnote disclosures under today’s guidance. ASU 2014‑15 is effective for the Company in the first quarter of 2016 with early adoption permitted. The Company does not believe the impact of adopting ASU 2014‑15 on its financial statements will be significant. In May 2014, the Financial Accounting Standards Board issued Accounting Standards Update No. 2014‑09, Revenue from Contracts with Customers (ASU 2014‑09) to provide guidance on revenue recognition. ASU 2014‑09 requires a company to recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. In doing so, companies will need to use more judgment and make more estimates than under today’s guidance. These may include identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation. In July 2015, the FASB voted to delay the effective date for this guidance. The guidance is effective for the Company in the first quarter of 2018. Early adoption up to the first quarter of 2017 is permitted. Upon adoption, ASU 2014‑09 can be applied retrospectively to all periods presented or only to the most current period presented with the cumulative effect of changes reflected in the opening balance of retained earnings in the most current period presented. The Company is currently evaluating the impact of adopting ASU 2014‑09 on its financial statements. In April 2015, the Financial Accounting Standards Board issued Accounting Standards Update No. 2015‑03, Interest—Imputation of Interest (Subtopic 835‑30): Simplifying the Presentation of Debt Issuance Costs (ASU 2015‑03). ASU 2015‑03 requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. ASU 2015‑03 is effective for the Company in the first quarter of 2016 with early adoption permitted. The Company does not believe the impact of adopting ASU 2015‑03 on its financial statements will be significant. In April 2015, the Financial Accounting Standards Board issued Accounting Standards Update No. 2015‑05, Intangibles—Goodwill and Other—Internal‑Use Software (Subtopic 350‑40): Customer’s Accounting for Fees Paid in a Cloud Computing Arrangement (ASU 2015‑05). ASU 2015‑05 provides guidance to clarify the customer’s accounting for fees paid in a cloud computing arrangement. ASU 2015‑05 is effective for the Company in the first quarter of 2016 with early adoption permitted. The Company is currently evaluating the impact of adopting ASU 2015‑05 on its financial statements. In July 2015, the Financial Accounting Standards Board issued Accounting Standards Update No. 2015-11, Inventory (Topic 330): Simplifying the Measurement of Inventory (ASU 2015-11). ASU 2015-11 provides guidance to simplify the measurement of inventory at the lower of cost and net realizable value under the first-in, first-out (“FIFO”) or average cost method. ASU 2015-11 is effective for the Company in the first quarter of 2017 with early adoption permitted. The Company does not believe the impact of adopting ASU 2015-11 on its financial statements will be significant.