Borrowings - Schedule of Asset-backed Borrowings at Amortized Cost (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2026	Dec. 31, 2025
Debt Instrument [Line Items]
Asset-backed borrowings at amortized cost	$ 2,088,453	$ 2,192,649
Asset-Backed Notes, At Amortized Cost \| Asset-Backed Notes
Debt Instrument [Line Items]
Initial amount issued	2,127,205	2,266,822
Asset-backed borrowings at amortized cost	2,088,453	2,192,649
Asset-Backed Notes, At Amortized Cost \| Initial Collateral \| Asset-Backed Notes
Debt Instrument [Line Items]
Collateral balance	2,194,269	2,342,596
Asset-Backed Notes, At Amortized Cost \| Current Collateral \| Asset-Backed Notes
Debt Instrument [Line Items]
Collateral balance	2,172,991	2,282,487
Oportun Issuance Trust 2026-A \| Asset-Backed Notes
Debt Instrument [Line Items]
Initial amount issued	484,990
Asset-backed borrowings at amortized cost	$ 482,573
Weighted average interest rate (as a percent)	5.25%
Original revolving period	2 years
Oportun Issuance Trust 2026-A \| Initial Collateral \| Asset-Backed Notes
Debt Instrument [Line Items]
Collateral balance	$ 502,450
Oportun Issuance Trust 2026-A \| Current Collateral \| Asset-Backed Notes
Debt Instrument [Line Items]
Collateral balance	508,985
Oportun Issuance Trust 2025-D \| Asset-Backed Notes
Debt Instrument [Line Items]
Initial amount issued	441,225	441,225
Asset-backed borrowings at amortized cost	$ 438,880	$ 438,410
Weighted average interest rate (as a percent)	5.69%	5.69%
Original revolving period	2 years	2 years
Oportun Issuance Trust 2025-D \| Initial Collateral \| Asset-Backed Notes
Debt Instrument [Line Items]
Collateral balance	$ 452,206	$ 452,206
Oportun Issuance Trust 2025-D \| Current Collateral \| Asset-Backed Notes
Debt Instrument [Line Items]
Collateral balance	458,165	461,986
Oportun Issuance Trust 2025-C \| Asset-Backed Notes
Debt Instrument [Line Items]
Initial amount issued	538,490	538,490
Asset-backed borrowings at amortized cost	$ 535,952	$ 535,394
Weighted average interest rate (as a percent)	5.23%	5.23%
Original revolving period	2 years	2 years
Oportun Issuance Trust 2025-C \| Initial Collateral \| Asset-Backed Notes
Debt Instrument [Line Items]
Collateral balance	$ 552,692	$ 552,692
Oportun Issuance Trust 2025-C \| Current Collateral \| Asset-Backed Notes
Debt Instrument [Line Items]
Collateral balance	559,579	559,689
Oportun Issuance Trust 2025-B \| Asset-Backed Notes
Debt Instrument [Line Items]
Initial amount issued	439,250	439,250
Asset-backed borrowings at amortized cost	$ 437,339	$ 436,850
Weighted average interest rate (as a percent)	5.57%	5.57%
Original revolving period	2 years	2 years
Oportun Issuance Trust 2025-B \| Initial Collateral \| Asset-Backed Notes
Debt Instrument [Line Items]
Collateral balance	$ 450,802	$ 450,802
Oportun Issuance Trust 2025-B \| Current Collateral \| Asset-Backed Notes
Debt Instrument [Line Items]
Collateral balance	456,344	456,345
Oportun Issuance Trust 2025-A \| Asset-Backed Notes
Debt Instrument [Line Items]
Initial amount issued		425,107
Asset-backed borrowings at amortized cost		$ 422,580
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]
Collateral balance		$ 439,775
Oportun Issuance Trust 2025-A \| Current Collateral \| Asset-Backed Notes
Debt Instrument [Line Items]
Collateral balance		445,314
Oportun Issuance Trust 2024-2 \| Asset-Backed Notes
Debt Instrument [Line Items]
Initial amount issued	223,250	223,250
Asset-backed borrowings at amortized cost	$ 53,226	$ 86,077
Weighted average interest rate (as a percent)	9.84%	8.34%
Oportun Issuance Trust 2024-2 \| Initial Collateral \| Asset-Backed Notes
Debt Instrument [Line Items]
Collateral balance	$ 236,119	$ 236,119
Oportun Issuance Trust 2024-2 \| Current Collateral \| Asset-Backed Notes
Debt Instrument [Line Items]
Collateral balance	63,684	102,446
Oportun Issuance Trust 2024-1 \| Asset-Backed Notes
Debt Instrument [Line Items]
Initial amount issued		199,500
Asset-backed borrowings at amortized cost		$ 28,626
Weighted average interest rate (as a percent)		12.07%
Oportun Issuance Trust 2024-1 \| Initial Collateral \| Asset-Backed Notes
Debt Instrument [Line Items]
Collateral balance		$ 211,002
Oportun Issuance Trust 2024-1 \| Current Collateral \| Asset-Backed Notes
Debt Instrument [Line Items]
Collateral balance		33,842
Other Asset Backed Borrowings \| Asset-Backed Notes
Debt Instrument [Line Items]
Asset-backed borrowings at amortized cost	140,483	244,712
Other Asset Backed Borrowings \| Current Collateral \| Asset-Backed Notes
Debt Instrument [Line Items]
Collateral balance	$ 126,234	$ 222,865