Summary of Significant Accounting Policies	3 Months Ended
Mar. 31, 2016
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and notes required by GAAP for complete financial statements. The financial statements include all adjustments (consisting only of normal recurring adjustments) that management believes are necessary for a fair presentation of the periods presented. The balance sheet as of December 31, 2015 was derived from the audited financial statements as of that date. These interim financial results are not necessarily indicative of results to be expected for the full year or any other period. These unaudited condensed consolidated financial statements and the notes accompanying them should be read in conjunction with the Company’s Annual Report on Form 10-K for the year ended December 31, 2015. During the first three months of fiscal 2016, the Company adopted Accounting Standards Update (ASU) 2016-06 “Derivatives and Hedging (Topic 815): Contingent Put and Call Options in Debt Instruments (a consensus of the FASB Emerging Issues Task Force)”on a modified retrospective basis. Pursuant to ASU 2016-06, a four-step decision sequence is required to assess whether contingent call (put) options that can accelerate the payment of principal on debt instruments are clearly and closely related to their debt hosts. The economic characteristics and risks of embedded derivatives that are not clearly and closed related to their debt hosts is a criteria pursuant to Topic 815 that requires embedded derivatives be separated from the host contract and accounted for separately as derivatives. There have been no adjustments to existing debt instruments as of the beginning of fiscal 2016 and no significant changes in our reported financial position or results of operations and cash flows as a result of the adoption of ASU 2016-06. Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”), that will supersede most existing revenue recognition guidance under US GAAP. The core principle of the guidance is that an entity should 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. Entities can choose to apply the standard using either the full retrospective approach or a modified retrospective approach. Entities electing the full retrospective adoption will apply the standard to each period presented in the financial statements. This means that entities will have to apply the new guidance as if it had been in effect since the inception of all its contracts with customers presented in the financial statements. Entities that elect the modified retrospective approach will apply the guidance retrospectively only to the most current period presented in the financial statements. This means that entities will have to recognize the cumulative effect of initially applying the new standard as an adjustment to the opening balance of retained earnings at the date of initial application. The new revenue standard will be applied to contracts that are in progress at the date of initial application. According to Accounting Standards Update No. 2015-14, Revenue from Contracts with Customers (“ASU 2015-14”), issued by the FASB in August 2015, the standard will be effective for annual and interim periods beginning after December 15, 2017. Company has yet to evaluate which adoption method it plans to use or the potential effect of the new standard on its consolidated financial statements. In August 2014, the FASB issued Accounting Standards Update No. 2014-15, Disclosure of Uncertainties about an Entity's Ability to Continue as a Going Concern (“ASU 2014-15”), which will require a reporting entity to evaluate, at each annual and interim reporting period, whether there are conditions or events that raise substantial doubt about the reporting entity's ability to continue as a going concern within one year after the date the financial statements are issued and provide related disclosures. The standard will be effective for annual periods ending after December 15, 2016, with early adoption permitted. The Company is in the process of evaluating the potential effect of the new standard on its consolidated financial statements. . In January 2016, the FASB issued ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities. ASU 2016-01 made modifications to how certain financial instruments should be measured and disclosed, including using the exit price notion when measuring the fair value, separating the presentation of financial assets and financial liabilities by measurement category on the balance sheet and eliminating the requirement to disclose the method and significant assumptions used to estimate the fair value that is required to be disclosed for financial instruments measured at amortized cost on the balance sheet. This guidance is effective for fiscal years beginning after December 15, 2017, including interim periods. The Company will evaluate the guidance and present the required disclosures in its consolidated financial statements at the time of adoption. In February 2016, the FASB issued ASU No. 2016-02, Leases. ASU 2016-02 is aimed at making leasing activities more transparent and comparable, and requires substantially all leases be recognized by lessees on their balance sheet as a right-of-use asset and corresponding lease liability, including leases currently accounted for as operating leases. ASU 2016-2 is effective for the Company’s interim and annual reporting periods during the year ending December 31, 2019, and all annual and interim reporting periods thereafter. Early adoption is permitted. The Company is currently evaluating the impact that the adoption of ASU 2016-2 will have on our consolidated financial statements and related disclosures. In March 2016, the FASB issued ASU No. 2016-09, Improvements to Employee Share-Based payment Accounting. ASU 2016-09 principally affects the recognition of excess tax benefits and deficiencies and the cash flow classification of share-based compensation related transactions. This guidance is effective for annual reporting periods beginning after December 15, 2016 and interim periods within those fiscal years with early adoption permitted. The Company will evaluate the guidance and present the required disclosures in its consolidated financial statements at the time of adoption. Principles of Consolidation The consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries, Sunesis Europe Limited, a United Kingdom corporation, and Sunesis Pharmaceuticals (Bermuda) Ltd., a Bermuda corporation, as well as a Bermuda limited partnership, Sunesis Pharmaceuticals International LP. All intercompany balances and transactions have been eliminated in consolidation. Segment Reporting Management has determined that the Company operates as a single reportable segment. Significant Estimates and Judgments The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the Company’s consolidated financial statements and accompanying notes thereto. Actual results could differ materially from these estimates. Estimates, assumptions and judgments made by management include those related to the valuation of equity and related instruments, debt instruments, revenue recognition, stock-based compensation and clinical trial accounting. Cash Equivalents and Marketable Securities Invoices for certain services provided to the Company are denominated in foreign currencies. To manage the risk of future movements in foreign exchange rates that would affect such amounts, the Company may purchase certain European currencies or highly-rated investments denominated in those currencies, subject to similar criteria as for other investments defined in the Company’s investment policy. There is no guarantee that the related gains and losses will substantially offset each other, and the Company may be subject to exchange gains or losses as currencies fluctuate from quarter to quarter. To date, the Company has purchased Euros and Euro-denominated obligations of foreign governments and corporate debt. As of March 31, 2016 and December 31, 2015, the Company held cash and investments denominated in Euros with an aggregate fair value of $0.8 million and $0.7 million, respectively. Any cash, cash equivalent and marketable securities balances denominated in foreign currencies are recorded at their fair value based on the current exchange rate as of each balance sheet date. The resulting exchange gains or losses and those from amounts payable for services originally denominated in foreign currencies are recorded in other income (expense), net in the statements of operations and comprehensive loss. Fair Value Measurements The Company measures cash equivalents, marketable securities and warrant liabilities at fair value on a recurring basis and warrants issued in connection with debt on a non-recurring basis using the following hierarchy to prioritize valuation inputs, in accordance with applicable GAAP: Level 1 - quoted prices (unadjusted) in active markets for identical assets and liabilities that can be accessed at the measurement date. Level 2 - inputs other than quoted prices included within Level 1 that are observable, either directly or indirectly. Level 3 - unobservable inputs. The Company’s Level 2 valuations of marketable securities are generally derived from independent pricing services based upon quoted prices in active markets for similar securities, with prices adjusted for yield and number of days to maturity, or based on industry models using data inputs, such as interest rates and prices that can be directly observed or corroborated in active markets. The fair value of the warrants issued in connection with a loan security agreement (see Note 7) is determined using the Black-Scholes model, which requires inputs such as the expected term of the warrants, share price volatility and risk-free interest rate. As some of these inputs are unobservable, and require significant analysis and judgment to measure, these variables are classified as Level 3. The Company does not measure cash, prepayments, accounts payable, accrued liabilities, deferred revenue and notes payable at fair value, as their carrying amounts approximated their fair value as of March 31, 2016 and December 31, 2015.

2. Summary of Significant Accounting Policies

Basis of Presentation

The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and notes required by GAAP for complete financial statements. The financial statements include all adjustments (consisting only of normal recurring adjustments) that management believes are necessary for a fair presentation of the periods presented. The balance sheet as of December 31, 2015 was derived from the audited financial statements as of that date. These interim financial results are not necessarily indicative of results to be expected for the full year or any other period. These unaudited condensed consolidated financial statements and the notes accompanying them should be read in conjunction with the Company’s Annual Report on Form 10-K for the year ended December 31, 2015.

During the first three months of fiscal 2016, the Company adopted Accounting Standards Update (ASU) 2016-06 “Derivatives and Hedging (Topic 815): Contingent Put and Call Options in Debt Instruments (a consensus of the FASB Emerging Issues Task Force)”on a modified retrospective basis. Pursuant to ASU 2016-06, a four-step decision sequence is required to assess whether contingent call (put) options that can accelerate the payment of principal on debt instruments are clearly and closely related to their debt hosts. The economic characteristics and risks of embedded derivatives that are not clearly and closed related to their debt hosts is a criteria pursuant to Topic 815 that requires embedded derivatives be separated from the host contract and accounted for separately as derivatives. There have been no adjustments to existing debt instruments as of the beginning of fiscal 2016 and no significant changes in our reported financial position or results of operations and cash flows as a result of the adoption of ASU 2016-06.

Recent Accounting Pronouncements

In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”), that will supersede most existing revenue recognition guidance under US GAAP. The core principle of the guidance is that an entity should 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. Entities can choose to apply the standard using either the full retrospective approach or a modified retrospective approach. Entities electing the full retrospective adoption will apply the standard to each period presented in the financial statements. This means that entities will have to apply the new guidance as if it had been in effect since the inception of all its contracts with customers presented in the financial statements. Entities that elect the modified retrospective approach will apply the guidance retrospectively only to the most current period presented in the financial statements. This means that entities will have to recognize the cumulative effect of initially applying the new standard as an adjustment to the opening balance of retained earnings at the date of initial application. The new revenue standard will be applied to contracts that are in progress at the date of initial application. According to Accounting Standards Update No. 2015-14, Revenue from Contracts with Customers (“ASU 2015-14”), issued by the FASB in August 2015, the standard will be effective for annual and interim periods beginning after December 15, 2017. Company has yet to evaluate which adoption method it plans to use or the potential effect of the new standard on its consolidated financial statements.

In August 2014, the FASB issued Accounting Standards Update No. 2014-15, Disclosure of Uncertainties about an Entity's Ability to Continue as a Going Concern (“ASU 2014-15”), which will require a reporting entity to evaluate, at each annual and interim reporting period, whether there are conditions or events that raise substantial doubt about the reporting entity's ability to continue as a going concern within one year after the date the financial statements are issued and provide related disclosures. The standard will be effective for annual periods ending after December 15, 2016, with early adoption permitted. The Company is in the process of evaluating the potential effect of the new standard on its consolidated financial statements. .

In January 2016, the FASB issued ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities. ASU 2016-01 made modifications to how certain financial instruments should be measured and disclosed, including using the exit price notion when measuring the fair value, separating the presentation of financial assets and financial liabilities by measurement category on the balance sheet and eliminating the requirement to disclose the method and significant assumptions used to estimate the fair value that is required to be disclosed for financial instruments measured at amortized cost on the balance sheet. This guidance is effective for fiscal years beginning after December 15, 2017, including interim periods. The Company will evaluate the guidance and present the required disclosures in its consolidated financial statements at the time of adoption.

In February 2016, the FASB issued ASU No. 2016-02, Leases. ASU 2016-02 is aimed at making leasing activities more transparent and comparable, and requires substantially all leases be recognized by lessees on their balance sheet as a right-of-use asset and corresponding lease liability, including leases currently accounted for as operating leases. ASU 2016-2 is effective for the Company’s interim and annual reporting periods during the year ending December 31, 2019, and all annual and interim reporting periods thereafter. Early adoption is permitted. The Company is currently evaluating the impact that the adoption of ASU 2016-2 will have on our consolidated financial statements and related disclosures.

In March 2016, the FASB issued ASU No. 2016-09, Improvements to Employee Share-Based payment Accounting. ASU 2016-09 principally affects the recognition of excess tax benefits and deficiencies and the cash flow classification of share-based compensation related transactions. This guidance is effective for annual reporting periods beginning after December 15, 2016 and interim periods within those fiscal years with early adoption permitted. The Company will evaluate the guidance and present the required disclosures in its consolidated financial statements at the time of adoption.

Principles of Consolidation

The consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries, Sunesis Europe Limited, a United Kingdom corporation, and Sunesis Pharmaceuticals (Bermuda) Ltd., a Bermuda corporation, as well as a Bermuda limited partnership, Sunesis Pharmaceuticals International LP. All intercompany balances and transactions have been eliminated in consolidation.

Segment Reporting

Management has determined that the Company operates as a single reportable segment.

Significant Estimates and Judgments

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the Company’s consolidated financial statements and accompanying notes thereto. Actual results could differ materially from these estimates. Estimates, assumptions and judgments made by management include those related to the valuation of equity and related instruments, debt instruments, revenue recognition, stock-based compensation and clinical trial accounting.

Cash Equivalents and Marketable Securities

Invoices for certain services provided to the Company are denominated in foreign currencies. To manage the risk of future movements in foreign exchange rates that would affect such amounts, the Company may purchase certain European currencies or highly-rated investments denominated in those currencies, subject to similar criteria as for other investments defined in the Company’s investment policy. There is no guarantee that the related gains and losses will substantially offset each other, and the Company may be subject to exchange gains or losses as currencies fluctuate from quarter to quarter. To date, the Company has purchased Euros and Euro-denominated obligations of foreign governments and corporate debt. As of March 31, 2016 and December 31, 2015, the Company held cash and investments denominated in Euros with an aggregate fair value of $0.8 million and $0.7 million, respectively. Any cash, cash equivalent and marketable securities balances denominated in foreign currencies are recorded at their fair value based on the current exchange rate as of each balance sheet date. The resulting exchange gains or losses and those from amounts payable for services originally denominated in foreign currencies are recorded in other income (expense), net in the statements of operations and comprehensive loss.

Fair Value Measurements

The Company measures cash equivalents, marketable securities and warrant liabilities at fair value on a recurring basis and warrants issued in connection with debt on a non-recurring basis using the following hierarchy to prioritize valuation inputs, in accordance with applicable GAAP:

Level 1 - quoted prices (unadjusted) in active markets for identical assets and liabilities that can be accessed at the measurement date.

Level 2 - inputs other than quoted prices included within Level 1 that are observable, either directly or indirectly.

Level 3 - unobservable inputs.

The Company’s Level 2 valuations of marketable securities are generally derived from independent pricing services based upon quoted prices in active markets for similar securities, with prices adjusted for yield and number of days to maturity, or based on industry models using data inputs, such as interest rates and prices that can be directly observed or corroborated in active markets.

The fair value of the warrants issued in connection with a loan security agreement (see Note 7) is determined using the Black-Scholes model, which requires inputs such as the expected term of the warrants, share price volatility and risk-free interest rate. As some of these inputs are unobservable, and require significant analysis and judgment to measure, these variables are classified as Level 3.

The Company does not measure cash, prepayments, accounts payable, accrued liabilities, deferred revenue and notes payable at fair value, as their carrying amounts approximated their fair value as of March 31, 2016 and December 31, 2015.