Borrowings - Schedule of Secured Financing Facilities (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025	Apr. 02, 2025
Debt Instrument [Line Items]
Facility Amount	$ 1,189,091
Secured financing	304,159	$ 199,384
Oportun PLW Trust
Debt Instrument [Line Items]
Facility Amount	367,741
Oportun PLW II Trust
Debt Instrument [Line Items]
Facility Amount	337,100
Oportun PLW III Trust
Debt Instrument [Line Items]
Facility Amount	187,500
Oportun PLW IV Trust
Debt Instrument [Line Items]
Facility Amount	246,750
Oportun PLW V Trust
Debt Instrument [Line Items]
Facility Amount	$ 50,000
Credit Facility
Debt Instrument [Line Items]
Weighted average interest rate (as a percent)	2.89%
Credit Facility \| Oportun PLW Trust
Debt Instrument [Line Items]
Secured financing	$ 70,994	73,078
Credit Facility \| Oportun PLW II Trust
Debt Instrument [Line Items]
Secured financing	83,494	68,916
Credit Facility \| Oportun PLW III Trust
Debt Instrument [Line Items]
Facility Amount			$ 187,500
Secured financing	65,077	35,051
Credit Facility \| Oportun PLW IV Trust
Debt Instrument [Line Items]
Secured financing	84,594	22,339
Credit Facility \| Oportun PLW V Trust
Debt Instrument [Line Items]
Facility Amount	50,000
Secured financing	$ 0	$ 0