v3.26.1
Cover - shares
 6 Months Ended
Jun. 30, 2026
Jul. 28, 2026
Cover [Abstract]    
Document Type 10-Q/A  
Document Quarterly Report true  
Document Period End Date Jun. 30, 2026  
Document Transition Report false  
Entity File Number 001-39797  
Entity Registrant Name Upstart Holdings, Inc.  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 46-4332431  
Entity Address, Address Line One 220 Park Road  
Entity Address, Address Line Two Suite 500  
Entity Address, City or Town Burlingame  
Entity Address, State or Province CA  
Entity Address, Postal Zip Code 94010  
City Area Code 833  
Local Phone Number 212-2461  
Title of 12(b) Security Common Stock, par value $0.0001 per share  
Trading Symbol UPST  
Security Exchange Name NASDAQ  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   97,313,046
Amendment Flag true  
Document Fiscal Year Focus 2026  
Document Fiscal Period Focus Q2  
Entity Central Index Key 0001647639  
Current Fiscal Year End Date --12-31  
Amendment Description Explanatory NoteThis Amendment No. 1 on Form 10-Q/A (“Amendment”) amends the Quarterly Report on Form 10-Q for Upstart Holdings, Inc. (“Company”) for the period ended June 30, 2026 filed with the Securities and Exchange Commission on August 4, 2026 (the “Original Form 10-Q”) to revise Part II, Item 1A, Risk Factors solely to correct a typographical error.The Company is amending its Original Form 10-Q to replace the fourth sentence in the last paragraph on page 92 with the following: “For example, as of June 30, 2026, the quarterly vintages of all personal loans excluding small dollar loans that originated in the second quarter of 2023 through the first quarter of 2024 and the fourth quarter of 2024 are forecasted to underperform relative to their target returns set at the time of loan origination.” In the Original Form 10-Q, the Company incorrectly referred to the time period "fourth quarter of 2025" in that sentence when, in fact, the time period should have been “fourth quarter of 2024” as correctly stated in the Credit Performance section of the Management’s Discussion and Analysis of Financial Condition and Results of Operations.Except for the items described above or contained in this Amendment, this Amendment speaks as of the original filing date of the Original Form 10-Q, and does not modify, amend or update any other item or disclosures in the Original Form 10-Q.