Description of Business and Basis of Presentation	3 Months Ended
Mar. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Description of Business and Basis of Presentation	1. Description of Business and Basis of Presentation Organization NantKwest, Inc. (the Company) was incorporated in Illinois on October 7, 2002 under the name ZelleRx Corporation. On January 22, 2010, the Company changed its name to Conkwest, Inc., and on July 10, 2015, the Company changed its name to NantKwest, Inc. In March 2014, the Company redomesticated from the State of Illinois to the State of Delaware and the Illinois Company ceased to exist. The Company is a pioneering clinical-stage immunotherapy biotechnology company headquartered in San Diego, California with certain operations in Culver City and El Segundo, California and Woburn, Massachusetts. The Company is focused on harnessing the power of the innate immune system by using the natural killer cell to treat cancer, infectious diseases and inflammatory diseases. A critical aspect of the Company’s strategy is to invest significantly in expanding the aNK platform and the development of the Company’s product candidates. The Company holds the exclusive right to commercialize activated natural killer (aNK) cells, a commercially viable natural killer cell-line, and a variety of genetically modified derivatives capable of killing cancer and virally infected cells. The Company owns corresponding U.S. and foreign composition and methods-of-use patents and applications covering the clinical use of aNK cells as a therapeutic to treat a spectrum of clinical conditions. The Company also licensed exclusive commercial rights to a portfolio of CD16 bearing aNK cells along with the corresponding U.S. and foreign composition and methods-of-use patents and applications covering the non-clinical use in laboratory testing of monoclonal antibodies, as well as clinical use as a therapeutic to treat cancers in combination with antibody products. The Company has licensed or sub-licensed its CD16 bearing aNK cell lines and intellectual property to numerous pharmaceutical and biotechnology companies for such non-clinical uses. The Company also licensed exclusive commercial rights to a unique HER2-specific receptor bearing aNK cell line along with the corresponding U.S. and foreign composition and methods-of-use patents and applications covering clinical use as a therapeutic to treat cancers. The Company retains exclusive worldwide rights to clinical and research data, intellectual property and know-how developed with the Company’s aNK cells, as well as the only clinical grade master cell bank. Unaudited Interim Financial Information The accompanying condensed consolidated balance sheet at March 31, 2018, the condensed consolidated statements of operations and comprehensive loss for the three months ended March 31, 2018 and 2017, the condensed consolidated statements of cash flows for the three months ended March 31, 2018 and 2017, and the condensed consolidated statement of stockholders’ equity for the three months ended March 31, 2018 have been prepared by management of the Company and have not been audited. These financial statements have been prepared on the same basis as the audited consolidated financial statements for the fiscal year ended December 31, 2017 and, in the opinion of management, include all normal recurring adjustments necessary for a fair statement of the Company’s results for the periods presented. These financial statements should be read in conjunction with the financial statements and notes thereto for the fiscal year ended December 31, 2017 included in the Company’s Annual Report on Form 10-K. Interim operating results are not necessarily indicative of operating results for the full year. The year-end consolidated balance sheet data was derived from audited financial statements, but does not include all disclosures required by accounting principles generally accepted in the United States of America (GAAP). Liquidity As of March 31, 2018, the Company had an accumulated deficit of approximately $526.0 million. The Company also had negative cash flow from operations of approximately $15.5 million during the three months ended March 31, 2018. The Company expects that it will likely need additional capital to further fund development of, and seek regulatory approvals for, its product candidates, and begin to commercialize any approved products. The Company is currently focused primarily on the development of immunotherapeutic treatments for cancers and debilitating viral infections using targeted cancer killing cell lines, and believes such activities will result in the Company’s continued incurrence of significant research and development and other expenses related to those programs. If the clinical trials for any of the Company’s product candidates fail or produce unsuccessful results and those product candidates do not gain regulatory approval, or if any of the Company’s product candidates, if approved, fail to achieve market acceptance, the Company may never become profitable. Even if the Company achieves profitability in the future, it may not be able to sustain profitability in subsequent periods. The Company intends to cover its future operating expenses through cash and cash equivalents and marketable debt securities on hand and through a combination of equity offerings, debt financings, government or other third-party funding, marketing and distribution arrangements and other collaborations, strategic alliances and licensing arrangements. Additional financing may not be available to the Company when needed and, if available, financing may not be obtained on terms favorable to the Company or its stockholders. While the Company expects its existing cash and cash equivalents and marketable debt securities will enable it to fund operations and capital expenditure requirements for at least the next twelve months, it may not have sufficient funds to reach commercialization. Failure to obtain adequate financing when needed may require the Company to delay, reduce, limit or terminate some or all of its development programs or future commercialization efforts or grant rights to develop and market product candidates that the Company might otherwise prefer to develop and market itself which could adversely affect the Company’s ability to operate as a going concern. If the Company raises additional funds from the issuance of equity securities, substantial dilution to existing stockholders may result. If the Company raises additional funds by incurring debt financing, the terms of the debt may involve significant cash payment obligations as well as covenants and specific financial ratios that may restrict the Company’s ability to operate its business.

1. Description of Business and Basis of Presentation

Organization

NantKwest, Inc. (the Company) was incorporated in Illinois on October 7, 2002 under the name ZelleRx Corporation. On January 22, 2010, the Company changed its name to Conkwest, Inc., and on July 10, 2015, the Company changed its name to NantKwest, Inc. In March 2014, the Company redomesticated from the State of Illinois to the State of Delaware and the Illinois Company ceased to exist. The Company is a pioneering clinical-stage immunotherapy biotechnology company headquartered in San Diego, California with certain operations in Culver City and El Segundo, California and Woburn, Massachusetts.

The Company is focused on harnessing the power of the innate immune system by using the natural killer cell to treat cancer, infectious diseases and inflammatory diseases. A critical aspect of the Company’s strategy is to invest significantly in expanding the aNK platform and the development of the Company’s product candidates.

The Company holds the exclusive right to commercialize activated natural killer (aNK) cells, a commercially viable natural killer cell-line, and a variety of genetically modified derivatives capable of killing cancer and virally infected cells. The Company owns corresponding U.S. and foreign composition and methods-of-use patents and applications covering the clinical use of aNK cells as a therapeutic to treat a spectrum of clinical conditions.

The Company also licensed exclusive commercial rights to a portfolio of CD16 bearing aNK cells along with the corresponding U.S. and foreign composition and methods-of-use patents and applications covering the non-clinical use in laboratory testing of monoclonal antibodies, as well as clinical use as a therapeutic to treat cancers in combination with antibody products. The Company has licensed or sub-licensed its CD16 bearing aNK cell lines and intellectual property to numerous pharmaceutical and biotechnology companies for such non-clinical uses. The Company also licensed exclusive commercial rights to a unique HER2-specific receptor bearing aNK cell line along with the corresponding U.S. and foreign composition and methods-of-use patents and applications covering clinical use as a therapeutic to treat cancers.

The Company retains exclusive worldwide rights to clinical and research data, intellectual property and know-how developed with the Company’s aNK cells, as well as the only clinical grade master cell bank.

Unaudited Interim Financial Information

The accompanying condensed consolidated balance sheet at March 31, 2018, the condensed consolidated statements of operations and comprehensive loss for the three months ended March 31, 2018 and 2017, the condensed consolidated statements of cash flows for the three months ended March 31, 2018 and 2017, and the condensed consolidated statement of stockholders’ equity for the three months ended March 31, 2018 have been prepared by management of the Company and have not been audited. These financial statements have been prepared on the same basis as the audited consolidated financial statements for the fiscal year ended December 31, 2017 and, in the opinion of management, include all normal recurring adjustments necessary for a fair statement of the Company’s results for the periods presented. These financial statements should be read in conjunction with the financial statements and notes thereto for the fiscal year ended December 31, 2017 included in the Company’s Annual Report on Form 10-K. Interim operating results are not necessarily indicative of operating results for the full year. The year-end consolidated balance sheet data was derived from audited financial statements, but does not include all disclosures required by accounting principles generally accepted in the United States of America (GAAP).

Liquidity

As of March 31, 2018, the Company had an accumulated deficit of approximately $526.0 million. The Company also had negative cash flow from operations of approximately $15.5 million during the three months ended March 31, 2018. The Company expects that it will likely need additional capital to further fund development of, and seek regulatory approvals for, its product candidates, and begin to commercialize any approved products. The Company is currently focused primarily on the development of immunotherapeutic treatments for cancers and debilitating viral infections using targeted cancer killing cell lines, and believes such activities will result in the Company’s continued incurrence of significant research and development and other expenses related to those programs. If the clinical trials for any of the Company’s product candidates fail or produce unsuccessful results and those product candidates do not gain regulatory approval, or if any of the Company’s product candidates, if approved, fail to achieve market acceptance, the Company may never become profitable. Even if the Company achieves profitability in the future, it may not be able to sustain profitability in subsequent periods. The Company intends to cover its future operating expenses through cash and cash equivalents and marketable debt securities on hand and through a combination of equity offerings, debt financings, government or other third-party funding, marketing and distribution arrangements and other collaborations, strategic alliances and licensing arrangements. Additional financing may not be available to the Company when needed and, if available, financing may not be obtained on terms favorable to the Company or its stockholders.

While the Company expects its existing cash and cash equivalents and marketable debt securities will enable it to fund operations and capital expenditure requirements for at least the next twelve months, it may not have sufficient funds to reach commercialization. Failure to obtain adequate financing when needed may require the Company to delay, reduce, limit or terminate some or all of its development programs or future commercialization efforts or grant rights to develop and market product candidates that the Company might otherwise prefer to develop and market itself which could adversely affect the Company’s ability to operate as a going concern. If the Company raises additional funds from the issuance of equity securities, substantial dilution to existing stockholders may result. If the Company raises additional funds by incurring debt financing, the terms of the debt may involve significant cash payment obligations as well as covenants and specific financial ratios that may restrict the Company’s ability to operate its business.