Organization	3 Months Ended
Mar. 31, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization	1. Organization Description of Business We, Principia Biopharma Inc. (“Principia”), are a late-stage biopharmaceutical company dedicated to bringing transformative therapies to patients with significant unmet medical needs in immune-mediated diseases. We were incorporated on October 6, 2008, began operations in February 2011, and are headquartered in South San Francisco, California.

The entire disclosure for organization, consolidation and basis of presentation of financial statements disclosure.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-URI http://asc.fasb.org/topic&trid=2122149

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-URI http://asc.fasb.org/topic&trid=2197479

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