Basis of Presentation and Recently Issued Accounting Standards	9 Months Ended
Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation and Recently Issued Accounting Standards	Basis of Presentation and Recently Issued Accounting Standards Basis of Presentation The accompanying unaudited interim consolidated financial statements of MacroGenics, Inc. (the Company) have been prepared in accordance with U.S. generally accepted accounting principles (GAAP) for interim financial information. The financial statements include all adjustments (consisting only of normal recurring adjustments) that the management of the Company believes are necessary for a fair presentation of the periods presented. These interim financial results are not necessarily indicative of results expected for the full fiscal year or for any subsequent interim period. The accompanying unaudited interim consolidated financial statements include the accounts of MacroGenics, Inc. and its wholly owned subsidiary, MacroGenics UK Limited. All intercompany accounts and transactions have been eliminated in consolidation. These consolidated financial statements and related notes should be read in conjunction with the financial statements and notes thereto included in the Company's 2016 Annual Report on Form 10-K filed with the Securities and Exchange Commission (SEC) on February 28, 2017. There have been no material changes to the significant accounting policies previously disclosed in the Company's 2016 Annual Report on Form 10-K other than as disclosed in the Recently Issued Accounting Standards section below. Recently Issued Accounting Standards In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2014-09, Revenue from Contracts with Customers (Topic 606) (ASU 2014-09). ASU 2014-09 will eliminate transaction- and industry-specific revenue recognition guidance under current GAAP and replace it with a principle-based approach for determining revenue recognition. ASU 2014-09 will require that companies recognize revenue based on the value of transferred goods or services as they occur in the contract. The ASU also will require additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. ASU 2014-09 is effective for annual reporting periods beginning after December 15, 2017 and interim periods therein, with early adoption permitted for interim and annual reporting periods beginning after December 15, 2016. ASU 2014-09 may be adopted either retrospectively or on a modified retrospective basis whereby ASU 2014-09 would be applied to new contracts and existing contracts with remaining performance obligations as of the effective date, with a cumulative catch-up adjustment recorded to beginning retained earnings at the effective date for existing contracts with remaining performance obligations. In 2016, the FASB issued ASU 2016-08, Revenue from Contracts with Customers: Principal versus Agent Considerations, ASU 2016-10, Revenue from Contracts with Customers: Identifying Performance Obligations and Licensing, and ASU 2016-12, Revenue from Contracts with Customers: Narrow-Scope Improvements and Practical Expedients to provide supplemental adoption guidance and clarification to ASU 2014-09. The effective date for these new standards is the same as the effective date and transition requirements for ASU 2014-09. The Company plans to adopt the new standard effective January 1, 2018 using the modified retrospective method with the cumulative effect of initially applying the new standard recognized in retained earnings at the date of initial adoption. Management has performed an initial review of each of the Company's collaboration and license agreements and assessed the potential effects of the standard on the Company's consolidated financial statements, accounting policies, and internal control over financial reporting. The Company does not anticipate that the adoption of the new revenue recognition standard will have a material impact on its contract revenues generated by its collaborative research and license agreements. In February 2016, the FASB issued ASU No. 2016-02, Leases (ASU 2016-02) that provides principles for the recognition, measurement, presentation and disclosure of leases for both lessees and lessors. ASU 2016-02 requires a lessee to recognize assets and liabilities on the balance sheet for operating leases and changes many key definitions, including the definition of a lease. ASU 2016-02 includes a short-term lease exception for leases with a term of 12 months or less, in which a lessee can make an accounting policy election not to recognize lease assets and lease liabilities. Lessees will continue to differentiate between finance leases (previously referred to as capital leases) and operating leases, using classification criteria that are substantially similar to the previous guidance. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years, with earlier application permitted. Entities are required to use a modified retrospective approach for leases that exist or are entered into after the beginning of the earliest comparative period in the financial statements. The Company is currently evaluating the effect of the standard on its consolidated financial statements and related disclosures. In March 2016, the FASB issued ASU 2016-09, Improvements to Employee Share-Based Payment Accounting (ASU 2016-09). This amendment addresses several aspects of the accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities and classification on the statement of cash flows. ASU 2016-09 is effective for fiscal years beginning after December 15, 2016, including interim periods within that year. The Company adopted ASU 2016-09 effective January 1, 2017 and has elected to continue to estimate the number of stock-based awards expected to vest, as permitted by ASU 2016-09, rather than electing to account for forfeitures as they occur. The adoption of this standard did not have a material impact on the Company's financial statements or related disclosures.

Basis of Presentation and Recently Issued Accounting Standards

Basis of Presentation

The accompanying unaudited interim consolidated financial statements of MacroGenics, Inc. (the Company) have been prepared in accordance with U.S. generally accepted accounting principles (GAAP) for interim financial information. The financial statements include all adjustments (consisting only of normal recurring adjustments) that the management of the Company believes are necessary for a fair presentation of the periods presented. These interim financial results are not necessarily indicative of results expected for the full fiscal year or for any subsequent interim period.

The accompanying unaudited interim consolidated financial statements include the accounts of MacroGenics, Inc. and its wholly owned subsidiary, MacroGenics UK Limited. All intercompany accounts and transactions have been eliminated in consolidation. These consolidated financial statements and related notes should be read in conjunction with the financial statements and notes thereto included in the Company's 2016 Annual Report on Form 10-K filed with the Securities and Exchange Commission (SEC) on February 28, 2017.

There have been no material changes to the significant accounting policies previously disclosed in the Company's 2016 Annual Report on Form 10-K other than as disclosed in the Recently Issued Accounting Standards section below.

Recently Issued Accounting Standards

In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2014-09, Revenue from Contracts with Customers (Topic 606) (ASU 2014-09). ASU 2014-09 will eliminate transaction- and industry-specific revenue recognition guidance under current GAAP and replace it with a principle-based approach for determining revenue recognition. ASU 2014-09 will require that companies recognize revenue based on the value of transferred goods or services as they occur in the contract. The ASU also will require additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. ASU 2014-09 is effective for annual reporting periods beginning after December 15, 2017 and interim periods therein, with early adoption permitted for interim and annual reporting periods beginning after December 15, 2016. ASU 2014-09 may be adopted either retrospectively or on a modified retrospective basis whereby ASU 2014-09 would be applied to new contracts and existing contracts with remaining performance obligations as of the effective date, with a cumulative catch-up adjustment recorded to beginning retained earnings at the effective date for existing contracts with remaining performance obligations. In 2016, the FASB issued ASU 2016-08, Revenue from Contracts with Customers: Principal versus Agent Considerations, ASU 2016-10, Revenue from Contracts with Customers: Identifying Performance Obligations and Licensing, and ASU 2016-12, Revenue from Contracts with Customers: Narrow-Scope Improvements and Practical Expedients to provide supplemental adoption guidance and clarification to ASU 2014-09. The effective date for these new standards is the same as the effective date and transition requirements for ASU 2014-09. The Company plans to adopt the new standard effective January 1, 2018 using the modified retrospective method with the cumulative effect of initially applying the new standard recognized in retained earnings at the date of initial adoption. Management has performed an initial review of each of the Company's collaboration and license agreements and assessed the potential effects of the standard on the Company's consolidated financial statements, accounting policies, and internal control over financial reporting. The Company does not anticipate that the adoption of the new revenue recognition standard will have a material impact on its contract revenues generated by its collaborative research and license agreements.

In February 2016, the FASB issued ASU No. 2016-02, Leases (ASU 2016-02) that provides principles for the recognition, measurement, presentation and disclosure of leases for both lessees and lessors. ASU 2016-02 requires a lessee to recognize assets and liabilities on the balance sheet for operating leases and changes many key definitions, including the definition of a lease. ASU 2016-02 includes a short-term lease exception for leases with a term of 12 months or less, in which a lessee can make an accounting policy election not to recognize lease assets and lease liabilities. Lessees will continue to differentiate between finance leases (previously referred to as capital leases) and operating leases, using classification criteria that are substantially similar to the previous guidance. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years, with earlier application permitted. Entities are required to use a modified retrospective approach for leases that exist or are entered into after the beginning of the earliest comparative period in the financial statements. The Company is currently evaluating the effect of the standard on its consolidated financial statements and related disclosures.

In March 2016, the FASB issued ASU 2016-09, Improvements to Employee Share-Based Payment Accounting (ASU 2016-09). This amendment addresses several aspects of the accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities and classification on the statement of cash flows. ASU 2016-09 is effective for fiscal years beginning after December 15, 2016, including interim periods within that year. The Company adopted ASU 2016-09 effective January 1, 2017 and has elected to continue to estimate the number of stock-based awards expected to vest, as permitted by ASU 2016-09, rather than electing to account for forfeitures as they occur. The adoption of this standard did not have a material impact on the Company's financial statements or related disclosures.