Summary of Significant Accounting Policies (Policies)	6 Months Ended
Jun. 30, 2020
Summary of Significant Accounting Policies
Unaudited Interim Financial Information	Unaudited Interim Financial Information The condensed consolidated financial statements of the Company included herein have been prepared, without audit, pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). Certain information and footnote disclosures normally included in financial statements prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) have been condensed or omitted from this report, as is permitted by such rules and regulations. Accordingly, these condensed consolidated financial statements should be read in conjunction with the financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2019 (the “Annual Report”). The unaudited condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiary, Editas Securities Corporation. All intercompany transactions and balances of the subsidiary have been eliminated in consolidation. In the opinion of management, the information furnished reflects all adjustments, all of which are of a normal and recurring nature, necessary for a fair presentation of the results for the reported interim periods. The Company considers events or transactions that occur after the balance sheet date but before the financial statements are issued to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. The three months ended June 30, 2020 and 2019 are referred to as the second quarter of 2020 and 2019, respectively. The results of operations for interim periods are not necessarily indicative of results to be expected for the full year or any other interim period.
Corporate Equity Securities	Corporate Equity Securities The Company classifies investments in equity securities that have a readily determinable fair value as marketable securities in the Company’s condensed consolidated balance sheets. The Company’s marketable securities are stated at fair value. Typically, the fair value of these securities is based on a quoted price for an identical equity security. If the equity security has a restriction that is determined to be an attribute of the security that would transfer to a market participant, the fair value of the security is measured based on the quoted price for an otherwise identical unrestricted equity security, adjusted for the effect of the restriction. The adjustment reflects the discount that a market participant would demand for the risk relating to the inability to dispose of the security for a specified period of time. That adjustment is based on the nature and duration of the restriction and the limitations imposed by the restriction to a buyer. The Company records changes in the fair value of its equity securities in “Other Income (Expense), net” in the Company’s condensed consolidated statement of operations.
Recent Accounting Pronouncements - Recently Adopted	Recent Accounting Pronouncements – Recently Adopted In June 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Statement Update (“ASU”) 2016-13, Financial Instruments-Credit Losses (“ASU 2016-13”) which was clarified and amended by the issuances of ASUs 2018-19, 2019-04, 2019-05 and 2019-11 in November 2018, April 2019, May 2019 and November 2019, respectively. The new standard requires that expected credit losses relating to financial assets measured on an amortized cost basis to be measured using an expected-loss model, replacing the current incurred-loss model, and recorded through an allowance for credit losses which is a valuation account that is deducted from the amortized cost basis of the financial asset. ASU 2016-13 requires evaluation of credit loss based on historical experience, current conditions and reasonable and supportable forecasts. The Company’s estimate of expected credit losses includes a measure of the expected risk of credit loss even if the risk is remote. When assessing financial assets for credit losses, the Company pools financial assets with similar risk characteristics and performs a collective evaluation. However, the Company is not required to measure expected credit losses in which historical credit loss information adjusted for current conditions and reasonable and supportable forecasts results in an expectation that nonpayment of the amortized cost basis is zero. At each reporting date, the Company will record an allowance for credit losses and reports it as credit loss expense which is included in “Other income (expense), net” in the Company’s condensed consolidated statement of operations. However subsequent increases or decreases in the fair value of available-for-sale securities that do not result in recognition or reversal of an allowance for credit loss or write-down will continue to be recorded in other comprehensive loss. The Company adopted the new standard and the related amendments on January 1, 2020 using a modified retrospective approach. The modified retrospective approach requires the Company to record a one-time adjustment to opening accumulated deficit as of the effective date. The Company concluded that there are no indicators of credit loss with respect to its available-for-sale debt securities which consist of U.S Treasury securities and government-agency bonds. The Company therefore did not record an allowance for credit losses or doubtful accounts upon adoption or during the first quarter of 2020. The adoption of ASU 2016-13 had no impact on the Company’s condensed consolidated financial statements. In August 2018, the FASB issued ASU 2018-15, Intangibles-Goodwill and Other-Internal Use Software: Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (“ASU 2018-15”). ASU 2018-15 aligns the requirements for capitalizing implementation costs incurred in a cloud computing arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. ASU 2018-15 was effective on January 1, 2020. The Company adopted ASU 2018-15 using the prospective transition approach, which allows the Company to change the accounting method without restating prior periods or recording cumulative adjustments. The adoption of ASU 2018-15 did not have a material impact on the Company’s condensed consolidated financial statements. In 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement (“ASU 2018-13”), which eliminates, adds, and modifies the disclosure requirements for fair value measurements. ASU 2018-13 was effective on January 1, 2020. The adoption of ASU 2018-13 results in additional disclosures related to the Company’s assets and liabilities that are valued based on Level 3 inputs and transfers between Level 1 and Level 2 fair value measurements. The adoption of ASU 2018-13 did not have a material impact on the Company’s financial statement footnote disclosures.

Summary of Significant Accounting Policies (Policies)

6 Months Ended

Jun. 30, 2020

Summary of Significant Accounting Policies

The condensed consolidated financial statements of the Company included herein have been prepared, without audit, pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). Certain information and footnote disclosures normally included in financial statements prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) have been condensed or omitted from this report, as is permitted by such rules and regulations. Accordingly, these condensed consolidated financial statements should be read in conjunction with the financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2019 (the “Annual Report”).

The unaudited condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiary, Editas Securities Corporation. All intercompany transactions and balances of the subsidiary have been eliminated in consolidation. In the opinion of management, the information furnished reflects all adjustments, all of which are of a normal and recurring nature, necessary for a fair presentation of the results for the reported interim periods. The Company considers events or transactions that occur after the balance sheet date but before the financial statements are issued to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. The three months ended June 30, 2020 and 2019 are referred to as the second quarter of 2020 and 2019, respectively. The results of operations for interim periods are not necessarily indicative of results to be expected for the full year or any other interim period.

Corporate Equity Securities

Corporate Equity Securities

The Company classifies investments in equity securities that have a readily determinable fair value as marketable securities in the Company’s condensed consolidated balance sheets. The Company’s marketable securities are stated at fair value. Typically, the fair value of these securities is based on a quoted price for an identical equity security. If the equity security has a restriction that is determined to be an attribute of the security that would transfer to a market participant, the fair value of the security is measured based on the quoted price for an otherwise identical unrestricted equity security, adjusted for the effect of the restriction. The adjustment reflects the discount that a market participant would demand for the risk relating to the inability to dispose of the security for a specified period of time. That adjustment is based on the nature and duration of the restriction and the limitations imposed by the restriction to a buyer. The Company records changes in the fair value of its equity securities in “Other Income (Expense), net” in the Company’s condensed consolidated statement of operations.

Recent Accounting Pronouncements - Recently Adopted

Recent Accounting Pronouncements – Recently Adopted

In June 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Statement Update (“ASU”) 2016-13, Financial Instruments-Credit Losses (“ASU 2016-13”) which was clarified and amended by the issuances of ASUs 2018-19, 2019-04, 2019-05 and 2019-11 in November 2018, April 2019, May 2019 and November 2019, respectively. The new standard requires that expected credit losses relating to financial assets measured on an amortized cost basis to be measured using an expected-loss model, replacing the current incurred-loss model, and recorded through an allowance for credit losses which is a valuation account that is deducted from the amortized cost basis of the financial asset. ASU 2016-13 requires evaluation of credit loss based on historical experience, current conditions and reasonable and supportable forecasts. The Company’s estimate of expected credit losses includes a measure of the expected risk of credit loss even if the risk is remote. When assessing financial assets for credit losses, the Company pools financial assets with similar risk characteristics and performs a collective evaluation. However, the Company is not required to measure expected credit losses in which historical credit loss information adjusted for

current conditions and reasonable and supportable forecasts results in an expectation that nonpayment of the amortized cost basis is zero. At each reporting date, the Company will record an allowance for credit losses and reports it as credit loss expense which is included in “Other income (expense), net” in the Company’s condensed consolidated statement of operations. However subsequent increases or decreases in the fair value of available-for-sale securities that do not result in recognition or reversal of an allowance for credit loss or write-down will continue to be recorded in other comprehensive loss. The Company adopted the new standard and the related amendments on January 1, 2020 using a modified retrospective approach. The modified retrospective approach requires the Company to record a one-time adjustment to opening accumulated deficit as of the effective date. The Company concluded that there are no indicators of credit loss with respect to its available-for-sale debt securities which consist of U.S Treasury securities and government-agency bonds. The Company therefore did not record an allowance for credit losses or doubtful accounts upon adoption or during the first quarter of 2020. The adoption of ASU 2016-13 had no impact on the Company’s condensed consolidated financial statements.

In August 2018, the FASB issued ASU 2018-15, Intangibles-Goodwill and Other-Internal Use Software: Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (“ASU 2018-15”). ASU 2018-15 aligns the requirements for capitalizing implementation costs incurred in a cloud computing arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. ASU 2018-15 was effective on January 1, 2020. The Company adopted ASU 2018-15 using the prospective transition approach, which allows the Company to change the accounting method without restating prior periods or recording cumulative adjustments. The adoption of ASU 2018-15 did not have a material impact on the Company’s condensed consolidated financial statements.

In 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement (“ASU 2018-13”), which eliminates, adds, and modifies the disclosure requirements for fair value measurements. ASU 2018-13 was effective on January 1, 2020. The adoption of ASU 2018-13 results in additional disclosures related to the Company’s assets and liabilities that are valued based on Level 3 inputs and transfers between Level 1 and Level 2 fair value measurements. The adoption of ASU 2018-13 did not have a material impact on the Company’s financial statement footnote disclosures.