Borrowings - Schedule of Asset-backed Notes at Fair Value (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2026	Dec. 31, 2025
Debt Instrument [Line Items]
Current balance	$ 137,778	$ 263,799
Asset-Backed Notes \| Asset-Backed Notes, At Fair Value
Debt Instrument [Line Items]
Initial amount issued	1,000,000	1,000,000
Current balance	137,778	263,799
Asset-Backed Notes \| Asset-Backed Notes, At Fair Value \| Initial Collateral
Debt Instrument [Line Items]
Collateral balance	1,025,521	1,025,521
Asset-Backed Notes \| Asset-Backed Notes, At Fair Value \| Current Collateral
Debt Instrument [Line Items]
Collateral balance	166,927	296,885
Asset-Backed Notes \| Oportun Issuance Trust (Series 2021-C)
Debt Instrument [Line Items]
Initial amount issued	500,000	500,000
Current balance	$ 91,504	$ 167,214
Weighted average interest rate (as a percent)	2.48%	2.48%
Original revolving period	3 years	3 years
Asset-Backed Notes \| Oportun Issuance Trust (Series 2021-C) \| Initial Collateral
Debt Instrument [Line Items]
Collateral balance	$ 512,762	$ 512,762
Asset-Backed Notes \| Oportun Issuance Trust (Series 2021-C) \| Current Collateral
Debt Instrument [Line Items]
Collateral balance	106,801	184,737
Asset-Backed Notes \| Oportun Issuance Trust (Series 2021-B)
Debt Instrument [Line Items]
Initial amount issued	500,000	500,000
Current balance	$ 46,274	$ 96,585
Weighted average interest rate (as a percent)	2.05%	2.06%
Original revolving period	3 years	3 years
Asset-Backed Notes \| Oportun Issuance Trust (Series 2021-B) \| Initial Collateral
Debt Instrument [Line Items]
Collateral balance	$ 512,759	$ 512,759
Asset-Backed Notes \| Oportun Issuance Trust (Series 2021-B) \| Current Collateral
Debt Instrument [Line Items]
Collateral balance	$ 60,126	$ 112,148