Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2017
Accounting Policies [Abstract]
Basis of Presentation and Use of Estimates	The accompanying financial statements have been prepared in accordance with U.S. generally accepted accounting principles (GAAP). To conform with GAAP, the preparation of our financial statements requires management to make judgments, assumptions, and estimates that affect the amounts reported in our financial statements and accompanying notes. Estimates are used for, but not limited to, accruals for clinical trial activity, other accrued liabilities, and assumptions used in determining stock-based compensation expense. We base our estimates on historical experience and on various other assumptions that we believe to be reasonable. Actual results could differ materially from those estimates.
Principles of Consolidation	Our consolidated financial statements include the financial position and results of operations of Immune Design Corp. and Immune Design Ltd., our wholly owned subsidiary. Immune Design Ltd. was incorporated in the United Kingdom in February 2016 and to date there have been no financial transactions or balances related to this entity.
Segments	We operate in one segment and use cash flow as the primary measure to manage our business and do not segment the business for internal reporting or decision-making purposes.
Offering Costs	Offering costs represent legal, accounting and other direct costs related to our efforts to raise capital through our follow-on public offerings in October 2017, September 2016 and April 2015 and for our initial public offering (IPO) in July 2014. These costs were deferred until completion of the follow-on public offerings and IPO, respectively, at which time they were reclassified to additional paid-in capital as a reduction of the proceeds.
Cash and Cash Equivalents	Cash equivalents are highly liquid investments with a maturity of 90 days or less at the date of purchase and primarily consist of investments in money market funds. In addition, we maintain cash balances with financial institutions in excess of insured limits and do not anticipate any losses on such cash balances.
Concentration of Risk	We limit our credit risk associated with cash and cash equivalents by placing our deposits with banks we believe are highly creditworthy and our investments with highly rated money market funds.
Short-term investments	Our short-term investments include funds invested in U.S. Treasury securities with a final maturity of each security of less than one year. All investments are classified as available-for-sale securities and are recorded at fair value based on quoted prices in active markets, with unrealized gains and losses excluded from earnings and reported in other comprehensive income (loss). Purchase premiums and discounts are recognized in interest income using the interest method over the terms of the securities. Realized gains and losses and declines in fair value that are deemed to be other than temporary are reflected in the consolidated statements of operations and comprehensive income (loss) using the specific-identification method.
Accounts Receivable	Accounts receivable are amounts due from other companies related primarily to licensing fees, product sales and research and development services.
Inventory	Inventory is recorded at the lower of cost or market. Cost includes amounts related to materials and labor, and is determined on a specific identification basis in a manner which approximates the first-in, first-out method. We record adjustments to inventory for potentially excess, obsolete, expired, or impaired items.
Property and Equipment	Property and equipment are stated at cost, net of accumulated depreciation. Depreciation is computed using the straight-line method over an estimated useful life that is generally three years, while leasehold improvements are amortized over the shorter of their estimated useful lives or the related lease term. Upon retirement or sale, the cost of assets disposed of and the related accumulated depreciation are removed from the accounts and any resulting gain or loss is credited or charged to operations. Maintenance and repairs are expensed as incurred. Asset improvements are capitalized.
Impairment of Long-Lived Assets	Long-lived assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of the assets might not be recoverable. Conditions that would necessitate an impairment assessment include a significant decline in the observable market value of an asset, a significant change in the extent or manner in which an asset is used, or any other significant adverse change that would indicate that the carrying amount of an asset is not recoverable.
Accrued Liabilities	Accrued liabilities represent accrued compensation including vacation accruals, unearned revenue and accrued expenses. As part of the process of preparing our consolidated financial statements, we are required to estimate our accrued professional services and research and development expenses. This process involves reviewing contracts and vendor agreements, communicating with our applicable personnel to identify services that have been performed on our behalf. We estimate the level of service performed and the associated cost incurred for the service when we have not yet been invoiced or otherwise notified of actual cost. We make estimates of our accrued expenses as of each balance sheet date in our consolidated financial statements based on facts and circumstances known to us. We base our expenses related to contract manufacturing and clinical trials on our estimates of the services received and efforts expended pursuant to contracts with multiple contract manufacturing organizations and clinical research organizations that conduct and manage supply and clinical trials on our behalf. In accruing service fees, we estimate the time period over which services will be performed and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from our estimate, we adjust the accrual accordingly. Although we do not expect our estimates to be materially different from amounts actually incurred, if our estimates of the status and timing of services performed differ from the actual status and timing of services performed, we may report amounts that are too high or too low in any particular period. To date, we have not experienced any significant adjustments to our estimates.
Leases and Deferred Rent	We have entered into lease agreements for laboratory and office facilities. These leases are classified as operating leases. Rent expense is recognized on a straight-line basis over the term of the lease. Incentives granted under our facilities leases, including allowances to fund leasehold improvements and rent escalations are accrued as deferred rent. Leasehold improvements funded by the lessor are capitalized and are recognized as reductions to rental expense on a straight-line basis over the term of the lease.
Revenue Recognition	We derive our revenue from collaboration and licensing agreements and the sale of products associated with material transfer, collaboration and supply agreements. Licensing fees, are recognized when the amounts are earned and determinable during the applicable period. We recognize up-front nonrefundable license fees when due under contractual agreements and when we do not have a continuing obligation to provide services related to the agreement. Revenue associated with nonrefundable up-front license fees under arrangements where the license fees and research and development activities cannot be accounted for as separate units of accounting is deferred and recognized as revenue on a straight-line basis over the expected term of our continued involvement in the research and development process. Revenues from the achievement of research and development milestones, if deemed substantive, are recognized as revenue when the milestones are achieved, and the milestone payments are due and collectible. If not deemed substantive, we recognize such milestones as revenue on a straight-line basis over the remaining expected term of continued involvement in the research and development process. Milestones are considered substantive if all of the following conditions are met: (1) the milestone is nonrefundable, (2) achievement of the milestone was not reasonably assured at the inception of the arrangement, (3) substantive effort is involved to achieve the milestone and (4) the amount of the milestone appears reasonable in relation to the effort expended, the other milestones in the arrangement and the related risk associated with the achievement of the milestone and any ongoing research and development or other services are priced at fair value. Payments received in advance of work performed are recorded as unearned revenue. Certain agreements from which we derive our revenue include multiple deliverables. We recognize the revenue for each deliverable at fair value determined to be the estimated selling price in cases when neither vendor specific objective evidence nor third-party evidence is available. Revenues derived from funding of development costs are recognized when the related costs are incurred and when collectability is reasonably assured. Revenue is recognized when all of the following criteria are met: (1) persuasive evidence of an arrangement exists, (2) delivery has occurred or services have been rendered, (3) the price to the customer is fixed or determinable and (4) collectability is reasonably assured. The evaluation of these revenue recognition criteria requires significant management judgment. For instance, we use judgment to assess collectability based on factors such as the customer’s creditworthiness and past collection history, if applicable. If we determine that collection of a payment is not reasonably assured, revenue recognition is deferred until receipt of payment. We also use judgment to assess whether a price is fixed or determinable including, but not limited to, reviewing contractual terms and conditions related to payment terms. Revenue from product sales of glucopyranosyl lipid A (GLA), a product from our GLAAS platforms, is recognized when the risk of loss has passed to the customer or deferred until such time that risk of loss has passed. All revenues associated from the sale of GLA products supplied by us are reported under product sales with the applicable costs reported under cost of product sales. Product sales consist of the direct costs associated with the manufacture and formulation of GLA, including costs to purchase raw materials, third-party contract manufacturing costs, assay testing and ongoing product stability testing. We consider significant revenue concentrations to be customers who account for 10% or more of total revenues generated by us during the periods presented.
Stock-Based Compensation	We account for stock-based compensation under the fair value method. Stock-based compensation costs related to employees and directors is measured at the grant date, based on the fair-value-based measurement of the award estimated using the Black-Scholes option-pricing model, and is recognized as expense over the requisite service period on a straight-line basis. Options granted to non-employee service providers are accounted for at estimated fair value using the Black-Scholes option-pricing model and are remeasured over the vesting term as earned. Prior to the Financial Accounting Standards Board (FASB) adoption of Accounting Standards Update (ASU) No. 2016-09 on January 1, 2017, stock-based compensation expense recognized was calculated based on awards ultimately expected to vest and was reduced for estimated forfeitures. Upon the FASB adoption of ASU No. 2016-09, effective January 1, 2017, we have elected to account for forfeitures as they occur. As of January 1, 2017, we had unrecorded forfeitures of $157,000. Upon adoption, we recognized this expense as an adjustment to retained earnings with a corresponding increase to additional paid-in-capital. In addition, under this guidance, on a prospective basis, companies will no longer record excess tax benefits and certain tax deficiencies in additional paid-in-capital. Instead, they will record all excess tax benefits and tax deficiencies as income tax expense or benefit in the income statement and eliminates the requirement that excess tax benefits be realized before companies can recognize them. As of January 1, 2017, we had an unrecognized excess tax benefit of $1.2 million and upon adoption, we recognized this excess tax benefit as a deferred tax asset with a corresponding increase to our deferred tax asset valuation allowance.
Research and Development	Research and development costs are expensed as incurred. Research and development costs primarily include personnel costs, materials and manufacturing to support clinical trials, fees paid to consultants and outside service providers, costs to conduct clinical trials and allocated overhead. Amounts incurred in connection with collaboration agreements are also included in research and development expense. Payments made prior to the receipt of goods or services to be used in research and development are deferred until the goods or services are received.
Income Taxes	Income taxes are accounted for under the liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to the differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and the operating loss and tax credit carry forwards. Valuation allowances are established when necessary to reduce deferred tax assets to the amount expected to be realized. Deferred tax assets and liabilities are measured at the balance sheet date using the enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in the period such tax rate changes are enacted. Our net deferred tax asset has been fully offset by a valuation allowance because of our history of losses. Any potential accrued interest and penalties related to unrecognized tax benefits within operations would be recorded as income tax expense. To date, there have been no interest or penalties charged to us related to the underpayment of income taxes.
Comprehensive Loss	Comprehensive loss is composed of net loss and other comprehensive income or loss that are excluded from net loss.
Subsequent Events	We consider 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.
Recent Accounting Pronouncements	In May 2014, the FASB issued ASU No. 2014-09 amending revenue recognition guidance and requiring more detailed disclosures to enable users of financial statements to understand the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. In August 2015, the FASB deferred the effective date of the revenue recognition guidance to reporting periods beginning after December 15, 2017. The new standard permits two methods of adoption: retrospectively to each prior reporting period presented (full retrospective method), or retrospectively with the cumulative effect of initially applying the guidance recognized at the date of initial application (the modified retrospective method). We currently anticipate adopting the new standard effective January 1, 2018, using the modified retrospective method. We will continue to monitor additional modifications, clarifications or interpretations undertaken by the FASB that may impact our current conclusions. We primarily derive our revenue from license and collaboration agreements. The consideration we are eligible to receive under these agreements includes upfront payments, research and development funding, milestone payments and royalties. Each license and collaboration agreement is unique and will be assessed separately under the five-step process under the new standard. The new revenue recognition standard differs from the current accounting standard in many respects, such as in the accounting for variable considerations and the measurement of progress toward completion of performance obligations. We performed a review of all of our ongoing license and collaboration agreements and based upon our assessment and given the nature of our arrangements and the related performance obligations, we determined there will be no impact on our financial position and results of operations as a result of the adoption of the standard on January 1, 2018, the date of adoption. In February 2016, FASB issued ASU 2016-02 related to lease accounting. This standard will require organizations that lease assets to recognize on the balance sheet the assets and liabilities for the rights and obligations created by those leases that are greater than 12 months in duration. The recognition, measurement, and presentation of expenses and cash flows arising from a lease by a lessee have not significantly changed from previous GAAP. There continues to be a differentiation between finance leases and operating leases, however, the principal difference from previous guidance is that the lease assets and lease liabilities arising from operating leases will be recognized on the balance sheets. For capital or finance leases, lessees will recognize amortization of the right-of-use asset separately from interest on the lease liability. For operating leases, lessees will recognize a single total lease expense. The standard is effective for public companies for the fiscal years and interim reporting periods beginning after December 15, 2018. We plan to adopt this new standard prospectively on January 1, 2019. We are evaluating the impact of the adoption of this standard on our consolidated financial statements. We expect that it will increase our lease assets and correspondingly increase our lease liabilities. In August 2016, the FASB issued ASU No. 2016-15 which provides new guidance on the classification of certain cash receipts and payments in the statement of cash flows. The new guidance is intended to reduce diversity in practice in how certain transactions are classified in the statement of cash flows. We will be required to adopt the new guidance beginning with the first fiscal quarter of 2018; early adoption is permitted. We are currently assessing the impact that the new guidance will have on its consolidated statements of cash flows. In November 2016, the FASB issued ASU No. 2016-18 that relates to restricted cash. The new guidance requires amounts generally described as restricted cash and restricted cash equivalents should be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. We will be required to revise our consolidated statements of cash flows to adopt the new guidance beginning with the first fiscal quarter of 2018; early adoption is permitted. Adoption of the new guidance will not have a significant impact on our financial position and results of operations. In May 2017, the FASB issued ASU No. 2017-09 to provide clarity and reduce both diversity in practice and cost and complexity when applying the guidance in Topic 718 about a change to the terms and conditions of a share-based payment award. The amendments in this update provide guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting in Topic 718. The amendments in this update are effective for annual periods, including interim periods within those annual periods, beginning after December 15, 2017. Early adoption is permitted, and applied prospectively to modifications that occur on or after the adoption date. We are currently reviewing and evaluating this recent update and plan to adopt on the required adoption date. For the year ended December 31, 2017, there were no modifications to the terms or conditions of a share-based payment award. In September 2017, the FASB issued ASU No. 2017-13 to amend revenue recognition (Topic 605), revenue from contracts with customers (Topic 606), leases (Topic 840), and leases (Topic 842) adding Securities and Exchange Commission (SEC) paragraphs pursuant to an SEC Staff Announcement made at the July 20, 2017 Emerging Issues Task Force (EITF) meeting. We are currently reviewing and evaluating this recent update and plan to adopt as required. For the year ended December 31, 2017, there were no modifications or changes incorporated with respect to this recently issued update.
Net Loss Per Share	Basic net loss per share is computed by dividing net loss by the weighted-average number of common shares outstanding during the period. Because of net losses recognized in each period, potential common shares issuable upon the exercise of outstanding stock options and warrants and the conversion of preferred shares in the IPO into common shares have not been reflected in the calculation of diluted net loss per share due to the anti-dilutive effect. Diluted net loss per share, therefore, does not differ from basic net loss per share.
Fair Value Measurement	We measure and record cash and cash equivalents and convertible preferred stock warrant liabilities at fair value in the accompanying financial statements. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability, or an exit price, in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value, is as follows: Level 1: Quoted prices in active markets for identical assets or liabilities. Level 2: Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3: Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Level 1 securities consist of highly liquid money market funds. The fair value of Level 1 assets has been determined using quoted prices in active markets for identical assets. In certain cases where there is limited activity or less transparency around inputs to valuation, securities are classified as Level 3 within the valuation hierarchy.