Borrowings - Schedule of Asset-backed Borrowings at Amortized Cost (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2025	Dec. 31, 2024	Jun. 05, 2025
Debt Instrument [Line Items]
Asset-backed borrowings at amortized cost	$ 1,605,597	$ 984,333
Asset-Backed Notes, At Amortized Cost \| Asset-Backed Notes
Debt Instrument [Line Items]
Initial note amount issued	1,484,497	620,140
Asset-backed borrowings at amortized cost	1,605,597	984,333
Asset-Backed Notes, At Amortized Cost \| Initial Collateral \| Asset-Backed Notes
Debt Instrument [Line Items]
Initial collateral balance	1,548,228	657,652
Asset-Backed Notes, At Amortized Cost \| Current Collateral \| Asset-Backed Notes
Debt Instrument [Line Items]
Initial collateral balance	1,695,922	1,043,689
Oportun Issuance Trust 2025-B \| Asset-Backed Notes
Debt Instrument [Line Items]
Initial note amount issued	439,250		$ 439,300
Asset-backed borrowings at amortized cost	$ 436,366
Weighted average interest rate (as a percent)	5.57%
Original revolving period	2 years
Oportun Issuance Trust 2025-B \| Initial Collateral \| Asset-Backed Notes
Debt Instrument [Line Items]
Initial collateral balance	$ 450,802
Oportun Issuance Trust 2025-B \| Current Collateral \| Asset-Backed Notes
Debt Instrument [Line Items]
Initial collateral balance	459,985
Oportun Issuance Trust 2025-A \| Asset-Backed Notes
Debt Instrument [Line Items]
Initial note amount issued	425,107
Asset-backed borrowings at amortized cost	$ 421,119
Weighted average interest rate (as a percent)	6.15%
Original revolving period	1 year
Oportun Issuance Trust 2025-A \| Initial Collateral \| Asset-Backed Notes
Debt Instrument [Line Items]
Initial collateral balance	$ 439,775
Oportun Issuance Trust 2025-A \| Current Collateral \| Asset-Backed Notes
Debt Instrument [Line Items]
Initial collateral balance	445,186
Oportun Issuance Trust 2024-2 \| Asset-Backed Notes
Debt Instrument [Line Items]
Initial note amount issued	223,250	223,250
Asset-backed borrowings at amortized cost	$ 128,954	$ 188,316
Weighted average interest rate (as a percent)	7.51%	6.99%
Oportun Issuance Trust 2024-2 \| Initial Collateral \| Asset-Backed Notes
Debt Instrument [Line Items]
Initial collateral balance	$ 236,119	$ 236,119
Oportun Issuance Trust 2024-2 \| Current Collateral \| Asset-Backed Notes
Debt Instrument [Line Items]
Initial collateral balance	153,422	213,802
Oportun Issuance Trust 2024-1 \| Asset-Backed Notes
Debt Instrument [Line Items]
Initial note amount issued	199,500	199,500
Asset-backed borrowings at amortized cost	$ 53,505	$ 92,385
Weighted average interest rate (as a percent)	9.68%	8.27%
Oportun Issuance Trust 2024-1 \| Initial Collateral \| Asset-Backed Notes
Debt Instrument [Line Items]
Initial collateral balance	$ 211,002	$ 211,002
Oportun Issuance Trust 2024-1 \| Current Collateral \| Asset-Backed Notes
Debt Instrument [Line Items]
Initial collateral balance	62,399	107,137
Oportun CL Trust 2023-A \| Asset-Backed Notes
Debt Instrument [Line Items]
Initial note amount issued	197,390	197,390
Asset-backed borrowings at amortized cost	$ 196,281	$ 195,855
Weighted average interest rate (as a percent)	10.05%	10.05%
Original revolving period	2 years	2 years
Oportun CL Trust 2023-A \| Initial Collateral \| Asset-Backed Notes
Debt Instrument [Line Items]
Initial collateral balance	$ 210,530	$ 210,530
Oportun CL Trust 2023-A \| Current Collateral \| Asset-Backed Notes
Debt Instrument [Line Items]
Initial collateral balance	219,690	219,717
Other Asset Backed Borrowings \| Asset-Backed Notes
Debt Instrument [Line Items]
Asset-backed borrowings at amortized cost	369,372	507,776
Other Asset Backed Borrowings \| Current Collateral \| Asset-Backed Notes
Debt Instrument [Line Items]
Initial collateral balance	$ 355,240	$ 503,032