Variable Interest Entities - Assets and Liabilities (Details) - USD ($) $ in Thousands		Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Dec. 31, 2020
Variable Interest Entity [Line Items]
Assets	[1]	$ 1,987,591	$ 1,820,455
Liabilities	[1]	1,111,087	1,013,377
Net Assets		876,504	807,078	$ 320,590	$ 300,252
Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Assets		675,973	342,025	675,973
Liabilities		122,228	49,314	122,228
Net Assets			292,711	$ 553,745
Variable Interest Entity, Not Primary Beneficiary | Securitizations and other
Variable Interest Entity [Line Items]
Assets		165,716	217,321
Liabilities		116,886	160,248
Net Assets		48,830	57,073
Maximum Exposure to Losses		$ 13,599	$ 15,503

[1] The following table presents information on assets and liabilities related to variable interest entities (“VIEs”) that are consolidated by Upstart Holdings, Inc. at December 31, 2021 and March 31, 2022. The assets in the table below may only be used to settle obligations of consolidated VIEs and are in excess of those obligations. The holders of the beneficial interests do not have recourse to the general credit of Upstart Holdings, Inc. The assets and liabilities in the table below include third-party assets and liabilities of consolidated VIEs and exclude intercompany balances that eliminate in consolidation. December 31,March 31,20212022AssetsCash $7,700 $407 Restricted cash79,561 75,527 Loans (at fair value)245,972 591,554  Other assets (includes $7,571 and $5,840 at fair value as of December 31, 2021 and March 31, 2022, respectively) 8,792 8,485 Total assets$342,025 $675,973 LiabilitiesBorrowings48,536 121,551 Other liabilities 778 677 Total liabilities$49,314 $122,228