Securitizations and Variable Interest Entities - Assets and Liabilities (Details) - USD ($) $ in Thousands		Dec. 31, 2021	Dec. 31, 2020
Variable Interest Entity [Line Items]
Assets	[1]	$ 1,820,455	$ 477,255
Liabilities	[1]	1,013,377	177,003
Net Assets		807,078	300,252
Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Assets		342,025	104,992
Liabilities		49,314	42,296
Net Assets		292,711	62,696
Variable Interest Entity, Primary Beneficiary | Warehouse entities
Variable Interest Entity [Line Items]
Assets		219,734	71,530
Liabilities		48,367	35,109
Net Assets		171,367	36,421
Variable Interest Entity, Primary Beneficiary | Majority-owned affiliates
Variable Interest Entity [Line Items]
Assets		7,571	17,219
Liabilities		507	7,187
Net Assets		7,064	10,032
Variable Interest Entity, Primary Beneficiary | Other consolidated VIEs
Variable Interest Entity [Line Items]
Assets		114,720	16,243
Liabilities		440	0
Net Assets		114,280	16,243
Variable Interest Entity, Not Primary Beneficiary | Securitizations and other
Variable Interest Entity [Line Items]
Assets		217,321	524,358
Liabilities		160,248	430,006
Net Assets		57,073	94,352
Maximum Exposure to Losses		$ 15,503	$ 26,141

[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, 2020 and 2021. 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,December 31,20202021AssetsCash $— $7,700 Restricted cash12,371 79,561 Loans (at fair value)75,373 245,972 Notes receivable and residual certificates (at fair value)17,219 7,571 Other assets29 1,221 Total assets$104,992 $342,025 LiabilitiesAccounts payable$83 $— Borrowings42,181 48,536 Other liabilities 32 778 Total liabilities$42,296 $49,314