Cover Page - USD ($)	12 Months Ended
	Dec. 31, 2022	Feb. 08, 2023	Jun. 30, 2022
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2022
Current Fiscal Year End Date	--12-31
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	2950 S. Delaware Street
Entity Address, Address Line Two	Suite 300
Entity Address, City or Town	San Mateo
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94403
City Area Code	650
Local Phone Number	204-1000
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Trading Symbol	UPST
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
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
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 2,234,352,139
Entity Common Stock, Shares Outstanding		81,386,429
Documents Incorporated by Reference	Portions of the registrant’s Definitive Proxy Statement relating to the 2023 Annual Meeting of Stockholders are incorporated by reference into Part II and III of this Annual Report on Form 10-K to the extent stated herein. Such Definitive Proxy Statement will be filed with the Securities and Exchange Commission within 120 days after the end of the registrant’s fiscal year ended December 31, 2022.
Amendment Flag	false
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	FY
Entity Central Index Key	0001647639