Basis of presentation and significant accounting policies (Policies)	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Basis of presentation	Basis of presentation The accompanying interim unaudited condensed consolidated financial statements have been prepared by us in accordance with accounting principles generally accepted in the United States of America (“US GAAP”). These condensed consolidated financial statements include our accounts and the accounts of our wholly-owned subsidiaries. All intercompany transactions have been eliminated in consolidation. Certain information and footnote disclosures normally included in our annual financial statements have been omitted. In the opinion of management, the unaudited interim financial statements reflect all adjustments, which with the exception of restructuring accruals described in Note 9, consisted of normal and recurring adjustments, necessary for the fair presentation of our financial position at June 30, 2018, results of our operations for the three and six months ended June 30, 2018 and 2017 and cash flows for the six months ended June 30, 2018 and 2017. The results for the three and six months ended June 30, 2018 are not necessarily indicative of future results. These condensed consolidated financial statements should be read in conjunction with the audited financial statements for the year ended December 31, 2017, which are contained in our Annual Report on Form 10-K for the year ended December 31, 2017 (“2017 Annual Report on Form 10-K”) that was filed with the Securities and Exchange Commission (“SEC”) on March 15, 2018.	Basis of Presentation Our consolidated financial statements include the accounts of OvaScience, Inc. and our wholly-owned subsidiaries. All intercompany transactions have been eliminated in consolidation. The financial statements are presented in United States dollars, our functional currency.
Use of estimates	Use of estimates and summary of significant accounting policies These condensed consolidated financial statements are presented in conformity with US GAAP, which requires management to make estimates and assumptions that affect the amounts reported in the condensed consolidated financial statements and accompanying notes. Actual results could differ from those estimates. Our significant accounting policies are described in Note 2, “Summary of Significant Accounting Policies,” in our 2017 Annual Report on Form 10-K.	Use of Estimates The preparation of consolidated financial statements in conformity with U.S. generally accepted accounting principles requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. We base those estimates on historical experience and on various assumptions that are believed to be reasonable under the circumstances. Actual results could differ from those estimates.
Net loss per share	Net loss per share Basic and diluted net loss per common share are calculated by dividing net loss by the weighted average number of shares outstanding during the period. Potentially dilutive shares, including outstanding stock options and unvested restricted stock units, are only included in the calculation of diluted net loss per share when their effect is dilutive.	Net Loss per Share Basic and diluted net loss per common share is calculated by dividing net loss by the weighted average number of shares outstanding during the period. Potentially dilutive shares, including outstanding stock options and unvested restricted stock, are only included in the calculation of diluted net loss per share when their effect is dilutive.
Recent accounting standards	Recent accounting pronouncements In June 2018, the Financial Accounting Standards Board ("FASB") issued ASU No. 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Non-employee Share-Based Payment Accounting. ASU 2018-07 is intended to reduce the cost and complexity and to improve financial reporting for non-employee share-based payments. The ASU expands the scope of Topic 718, Compensation-Stock Compensation (which currently only includes share-based payments to employees), to include share-based payments issued to non-employees for goods or services. Consequently, the accounting for share-based payments to non-employees and employees will be substantially aligned. This update is effective for annual and interim periods beginning after December 15, 2018 with early adoption permitted. Upon transition, entities will remeasure unsettled liability-classified awards and any unmeasured equity-classified awards for non-employees at fair value as of the adoption date. A cumulative-effect adjustment to retained earnings will be required as of the beginning of the fiscal year of adoption. We are currently assessing the impact ASU 2016-13 will have on our consolidated financial statements and footnote disclosures thereto. In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230) - Restricted Cash. ASU 2016-18 requires that a statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. This update is effective for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years using a retrospective transition method to each period presented. The Company adopted this standard as of January 1, 2018 on a retrospective basis, which resulted in the recast of the prior reporting period in the statement of cash flows. For the six months ended June 30, 2018 and 2017, $0.8 million and $0.8 million, respectively, of restricted cash is included in the total of cash and restricted cash balance at the end of period. A reconciliation of cash and restricted cash from our condensed consolidated statement of cash flows to the amounts reported within our condensed consolidated balance sheet is also included in a table below our condensed consolidated statement of cash flows. In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments. ASU 2016-15 requires changes in the presentation of debt prepayment or debt extinguishment costs, contingent consideration payments made after a business combination, proceeds from the settlement of insurance claims, proceeds from the settlement of corporate-owned life insurance policies and distributions received from equity method investees. This update is effective for annual and interim periods beginning after December 15, 2017 using a retrospective transition method to each period presented. We adopted this standard as of January 1, 2018 with no material impact on our consolidated financial statements. In June 2016, the FASB issued ASU No. 2016-13, Measurement of Credit Losses on Financial Instruments, which amends the impairment model by requiring entities to use a forward-looking approach based on expected losses rather than incurred losses to estimate credit losses on certain types of financial instruments. This may result in the earlier recognition of allowances for losses. The guidance is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years, with early adoption permitted. We are currently assessing the impact ASU 2016-13 will have on our consolidated financial statements and footnote disclosures thereto. In February 2016, the FASB issued ASU No. 2016-02, Leases, which is intended to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and disclosing key information about leasing arrangements. Under ASU 2016-02, a lessee will be required to recognize assets and liabilities for both operating and financing leases with lease terms of more than 12 months. The amendment is effective for annual periods beginning after December 15, 2018, and interim periods within those annual periods. Early adoption is permitted. In July 2018, the FASB issued ASU 2018-11, Leases, to address two requirements of ASU 2016-02. ASU 2018-11 allows entities to recognize a cumulative-effect adjustment from the application of ASU 2016-02 to the opening balance of retained earnings in the period of adoption. In addition, ASU 2018-11 provides lessors with a practical expedient to not separate non-lease components from the associated lease component if certain conditions are met. We are currently assessing the impact ASU 2016-02 will have on our consolidated financial statements and footnote disclosures thereto. ASU 2014-09, Revenue from Contracts with Customers, amends the guidance for accounting for revenue from contracts with customers. ASU 2014-09 supersedes the revenue recognition requirements in ASC Topic 605, Revenue Recognition, and creates a new Topic 606, Revenue from Contracts with Customers. This guidance was effective for the Company on January 1, 2018. Two adoption methods are permitted: retrospectively to all prior reporting periods presented, with certain practical expedients permitted; or retrospectively with the cumulative effect of initially adopting the ASU 2014-09 recognized at the date of initial application. We adopted ASU 2014-09 effective January 1, 2018 and elected to adopt ASU 2014-09 using the modified retrospective approach and applied the standard only to contracts that had not yet been completed as of January 1, 2018. The impact under this methodology to our previously reported revenues is insignificant in the periods reported, and therefore the Company did not record a cumulative catch-up to deferred revenue and accumulated deficit upon adoption of the new standard on January 1, 2018.	In May 2017, the FASB issued ASU No. 2017-09, Compensation - Stock Compensation (Topic 718) - Scope of Modification Accounting. ASU 2017-09 clarifies the term modification and provides guidance on when to apply modification accounting, specifically when changes to the terms or conditions of a share-based payment occur. Entities should account for the effects of a modification unless all of the following conditions are met: (1) there is no change in the fair value of the award, (2) there is no change in the vesting conditions, and (3) there is no change in classification of the award as liability or equity. We adopted ASU 2017-09 for the period ending June 30, 2017, and the adoption of ASU 2017-09 did not have a material impact on our financial statements and the footnote disclosures thereto. In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230) - Restricted Cash. ASU 2016-18 requires that a statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. This update is effective for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years using a retrospective transition method to each period presented. Early adoption is permitted. We do not believe the adoption of ASU 2016-18 will have a material impact on our consolidated financial statements. In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments. ASU 2016-15 requires changes in the presentation of debt prepayment or debt extinguishment costs, contingent consideration payments made after a business combination, proceeds from the settlement of insurance claims, proceeds from the settlement of corporate-owned life insurance policies and distributions received from equity method investees. This update is effective for annual and interim periods beginning after December 15, 2017 using a retrospective transition method to each period presented. Early adoption is permitted. We do not believe the adoption of ASU 2016-15 will have a material impact on our consolidated financial statements. In February 2016, the FASB issued ASU No. 2016-02, Leases, which is intended to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and disclosing key information about leasing arrangements. Under ASU 2016-02, a lessee will be required to recognize assets and liabilities for both operating and financing leases with lease terms of more than 12 months. In addition, ASU 2016-02 requires the use of the modified retrospective method, which will require adjustment to all comparative periods presented in the consolidated financial statements. The amendment is effective for annual periods beginning after December 15, 2018, and interim periods within those annual periods. Early adoption is permitted. We are currently assessing the impact ASU 2016-02 will have on our consolidated financial statements and footnote disclosures thereto. In August 2015, the FASB issued ASU No. 2015-14 Revenue from Contracts with Customers, which defers the effective date of ASU No. 2014-09 by one year. ASU 2014-09 amends the guidance for accounting for revenue from contracts with customers. ASU 2014-09 supersedes the revenue recognition requirements in ASC Topic 605, Revenue Recognition, and creates a new Topic 606, Revenue from Contracts with Customers. This guidance is now effective for fiscal years beginning after December 15, 2017, with early adoption permitted for annual periods beginning after December 15, 2016. Two adoption methods are permitted: retrospectively to all prior reporting periods presented, with certain practical expedients permitted; or retrospectively with the cumulative effect of initially adopting the ASU 2014-09 recognized at the date of initial application. We will adopt ASU 2015-14 as of January 1, 2018, using the modified retrospective approach and will apply the standard only to contracts that have not yet been completed as of the adoption date. We will report new disclosures required by this guidance within our Form 10-Q for the interim period ending March 31, 2018. The impact under this methodology to our previously reported revenues is insignificant in the periods reported, with no effect to reported revenues in the fiscal year ended December 31, 2017.