Condensed Consolidated Statements of Operations and Comprehensive Income - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenue:
Revenue from fees, net		$ 801,275	$ 228,600	$ 159,847
Interest income and fair value adjustments, net	[1]	47,314	4,816	4,342
Total revenue		848,589	233,416	164,189
Operating expenses:
Sales and marketing		333,453	99,659	93,175
Customer operations		117,579	37,581	24,947
Engineering and product development		133,999	38,802	18,777
General, administrative, and other		122,677	45,609	31,865
Total operating expenses		707,708	221,651	168,764
Income (loss) from operations		140,881	11,765	(4,575)
Other income (expense)		(5,174)	5,549	1,036
Expense on warrants and convertible notes, net		(1,976)	(11,364)	(1,407)
Net income (loss) before income taxes		133,731	5,950	(4,946)
Provision (benefit) for income taxes		(1,712)	371	74
Net income (loss) before attribution to noncontrolling interests		135,443	5,579	(5,020)
Net loss attributable to noncontrolling interests		0	(404)	(4,554)
Net income (loss) attributable to Upstart Holdings, Inc. common stockholders		$ 135,443	$ 5,983	$ (466)
Net income (loss) per share attributable to Upstart Holdings, Inc. common stockholders, basic (in dollars per share)		$ 1.73	$ 0	$ (0.03)
Net income (loss) per share attributable to Upstart Holdings, Inc. common stockholders, diluted (in dollars per share)		$ 1.43	$ 0	$ (0.03)
Weighted-average number of shares outstanding used in computing net income (loss) per share attributable to Upstart Holdings, Inc. common stockholders, basic (in shares)		78,106,359	17,513,670	14,335,611
Weighted-average number of shares outstanding used in computing net income (loss) per share attributable to Upstart Holdings, Inc. common stockholders, diluted (in shares)		94,772,641	17,513,670	14,335,611

[1] Includes $2,963 and $1,014 from related parties expense and $7,400 and $4,238 of related parties fair value adjustments for the years ended December 31, 2019 and 2020, respectively.