Organization	12 Months Ended
Dec. 31, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization	Note 1. Organization Description of Business Arcus Biosciences, Inc. (the Company) is a clinical-stage biopharmaceutical company focused on creating best-in-class cancer therapies. The Company’s initial focus has been on well-characterized biological pathways with significant scientific data supporting their importance. Since its inception in 2015, the Company has built a robust and highly efficient drug discovery capability to create highly differentiated small molecules, which the Company is developing in combination with its in-licensed monoclonal antibodies through rationally designed, indication-specific clinical trial designs. The Company currently has four investigational products in clinical development: domvanalimab (formerly referred to as AB154), etrumadenant (formerly referred to as AB928), AB680, and zimberelimab (formerly referred to as AB122).

The entire disclosure for the nature of an entity's business, major products or services, principal markets including location, and the relative importance of its operations in each business and the basis for the determination, including but not limited to, assets, revenues, or earnings. For an entity that has not commenced principal operations, disclosures about the risks and uncertainties related to the activities in which the entity is currently engaged and an understanding of what those activities are being directed toward.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e5967-108592

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-URI http://asc.fasb.org/topic&trid=2134479

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