Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Revenue:
Revenue from fees, net	$ 258,345	$ 187,297	$ 572,327	$ 303,467
Interest income and fair value adjustments, net	(30,183)	6,649	(34,029)	11,824
Total revenue	228,162	193,946	538,298	315,291
Operating expenses:
Sales and marketing	105,212	75,916	238,661	125,292
Customer operations	51,072	24,164	99,479	41,552
Engineering and product development	57,045	31,431	107,036	50,419
General, administrative, and other	46,940	26,141	90,396	46,160
Total operating expenses	260,269	157,652	535,572	263,423
Income (loss) from operations	(32,107)	36,294	2,726	51,868
Other income (expense)	2,260	2	138	(5,249)
Net income (loss) before income taxes	(29,847)	36,296	2,864	46,619
(Benefit) provision for income taxes	24	(988)	43	(767)
Net income (loss)	$ (29,871)	$ 37,284	$ 2,821	$ 47,386
Net income (loss) per share, basic (in dollars per share)	$ (0.36)	$ 0.49	$ 0.03	$ 0.63
Net income (loss) per share, diluted (in dollars per share)	$ (0.36)	$ 0.39	$ 0.03	$ 0.51
Weighted-average common shares outstanding used to calculate net income per share attributable to Upstart Holdings, Inc. common stockholders, basic (in shares)	83,833,963	76,674,129	84,031,109	75,160,037
Weighted-average common shares outstanding used to calculate net income per share attributable to Upstart Holdings, Inc. common stockholders, diluted (in shares)	83,833,963	94,802,123	94,509,060	93,193,153