Borrowings - Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Debt Disclosure [Abstract]
Remainder of 2021	$ 20,500
2022	16,357
2023	5,071
2024	0
2025	0
Total	$ 41,928	$ 62,681

Long-term and Short-term Debt, Maturity, Remainder Of The Fiscal Year

No definition available.

Name:	upst_LongTermAndShortTermDebtMaturityRemainderOfTheFiscalYear
Namespace Prefix:	upst_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant