Description of Business	9 Months Ended
Description of Business	Sep. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	Description of Business Guardant Health, Inc., or the Company, is a leading precision oncology company focused on guarding wellness and giving every person more time free from cancer. The Company is transforming patient care by providing critical insights into what drives disease through its advanced blood and tissue tests, and real-world data. The Company's tests help improve outcomes across all stages of care, including screening to find cancer early, monitoring for recurrence in early-stage cancer, and helping doctors select the best treatment for patients with advanced cancer. For patients with advanced stage cancer, the Company has commercially launched Guardant360 LDT and Guardant360 CDx, the first comprehensive liquid biopsy test approved by the U.S. Food and Drug Administration, or the FDA, to provide tumor mutation profiling with solid tumors and to be used as a companion diagnostic in connection with non-small cell lung cancer, or NSCLC, and breast cancer. The Company has also launched the Guardant360 TissueNext tissue test for advanced-stage cancer, Guardant Reveal blood test to detect residual and recurring disease in early-stage colorectal, breast and lung cancer patients, and Guardant360 Response blood test to predict patient response to immunotherapy or targeted therapy eight weeks earlier than current standard-of-care imaging. The Company also collaborates with biopharmaceutical companies in clinical studies by providing the above-mentioned tests, as well as the GuardantOMNI blood test for advanced-stage cancer, and the GuardantINFINITY blood test, a next-generation smart liquid biopsy that provides new, multi-dimensional insights into the complexities of tumor molecular profiles and immune response to advance cancer research and therapy development. Using data collected from its tests, the Company has also developed its GuardantINFORM platform to help biopharmaceutical companies accelerate precision oncology drug development through the use of this in-silico research platform to unlock further insights into tumor evolution and treatment resistance across various biomarker-driven cancers. For early cancer detection, in May 2022, the Company launched the Shield LDT test to address the needs of individuals eligible for colorectal cancer screening. From a simple blood draw, Shield uses a novel multimodal approach to detect colorectal cancer signals in the bloodstream, including DNA that is shed by tumors. In December 2022, the Company announced that the ECLIPSE study, a registrational study evaluating the performance of its Shield blood test for detecting colorectal cancer in average-risk adults, met co-primary endpoints. In addition, in March 2023, the Company submitted a premarket approval application, or PMA, for its Shield blood test to the FDA. In July 2024, the Company received FDA approval of its Shield blood test for colorectal cancer screening in adults age 45 and older who are at average risk for the disease, and in August 2024, the Company's Shield blood test became commercially available in the U.S. as the first blood test approved by the FDA for primary colorectal cancer screening, meaning healthcare providers can offer Shield in a manner similar to all other non-invasive methods recommended in screening guidelines. Shield is also the first blood test for colorectal cancer screening that meets coverage requirements by Medicare. The Company was incorporated in Delaware in December 2011 and is headquartered in Palo Alto, California.