Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Revenue:
Revenue from fees, net	$ 179,348	$ 210,421	$ 751,675	$ 513,888
Interest income and fair value adjustments, net	(22,115)	18,029	(56,144)	29,853
Total revenue	157,233	228,450	695,531	543,741
Operating expenses:
Sales and marketing	56,362	93,346	295,023	218,638
Customer operations	45,028	34,978	144,507	76,530
Engineering and product development	66,182	37,085	173,218	87,504
General, administrative, and other	47,752	34,442	138,148	80,602
Total operating expenses	215,324	199,851	750,896	463,274
Income (loss) from operations	(58,091)	28,599	(55,365)	80,467
Other income (expense)	1,880	(754)	2,018	(6,003)
Net income (loss) before income taxes	(56,211)	27,845	(53,347)	74,464
(Benefit) provision for income taxes	12	(1,268)	55	(2,035)
Net income (loss)	$ (56,223)	$ 29,113	$ (53,402)	$ 76,499
Net income (loss) per share, basic (in dollars per share)	$ (0.69)	$ 0.37	$ (0.64)	$ 1.00
Net income (loss) per share, diluted (in dollars per share)	$ (0.69)	$ 0.30	$ (0.64)	$ 0.81
Weighted-average common shares outstanding used to calculate net income per share attributable to Upstart Holdings, Inc. common stockholders, basic (in shares)	81,672,099	79,392,600	83,236,131	76,586,395
Weighted-average common shares outstanding used to calculate net income per share attributable to Upstart Holdings, Inc. common stockholders, diluted (in shares)	81,672,099	96,057,210	83,236,131	94,165,325