Borrowings - Schedule of Asset-backed Notes (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Current balance	$ 1,386,695	$ 1,780,005
Asset-Backed Notes
Debt Instrument [Line Items]
Original Balance	2,475,000	2,754,412
Current balance	1,386,695	1,780,005
Asset-Backed Notes | Initial Collateral
Debt Instrument [Line Items]
Collateral balance	2,540,569	2,834,687
Asset-Backed Notes | Current Collateral
Debt Instrument [Line Items]
Collateral balance	1,498,910	1,976,039
Asset-Backed Notes | Oportun Issuance Trust (Series 2022-3)
Debt Instrument [Line Items]
Original Balance	300,000	300,000
Current balance	$ 72,982	$ 145,732
Weighted average interest rate (as a percent)	10.86%	9.34%
Asset-Backed Notes | Oportun Issuance Trust (Series 2022-3) | Initial Collateral
Debt Instrument [Line Items]
Collateral balance	$ 310,993	$ 310,993
Asset-Backed Notes | Oportun Issuance Trust (Series 2022-3) | Current Collateral
Debt Instrument [Line Items]
Collateral balance	83,284	165,079
Asset-Backed Notes | Oportun Issuance Trust (Series 2022-2)
Debt Instrument [Line Items]
Original Balance	400,000	400,000
Current balance	$ 56,595	$ 135,825
Weighted average interest rate (as a percent)	10.40%	8.46%
Asset-Backed Notes | Oportun Issuance Trust (Series 2022-2) | Initial Collateral
Debt Instrument [Line Items]
Collateral balance	$ 410,212	$ 410,212
Asset-Backed Notes | Oportun Issuance Trust (Series 2022-2) | Current Collateral
Debt Instrument [Line Items]
Collateral balance	65,372	156,027
Asset-Backed Notes | Oportun Issuance Trust (Series 2022-A)
Debt Instrument [Line Items]
Original Balance	400,000	400,000
Current balance	$ 324,055	$ 390,755
Weighted average interest rate (as a percent)	5.53%	5.44%
Debt term	2 years	2 years
Asset-Backed Notes | Oportun Issuance Trust (Series 2022-A) | Initial Collateral
Debt Instrument [Line Items]
Collateral balance	$ 410,211	$ 410,211
Asset-Backed Notes | Oportun Issuance Trust (Series 2022-A) | Current Collateral
Debt Instrument [Line Items]
Collateral balance	343,150	415,448
Asset-Backed Notes | Oportun Issuance Trust (Series 2021-C)
Debt Instrument [Line Items]
Original Balance	500,000	500,000
Current balance	$ 483,332	$ 459,212
Weighted average interest rate (as a percent)	2.48%	2.47%
Debt term	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	519,381	519,612
Asset-Backed Notes | Oportun Issuance Trust (Series 2021-B)
Debt Instrument [Line Items]
Original Balance	500,000	500,000
Current balance	$ 371,047	$ 466,317
Weighted average interest rate (as a percent)	2.05%	2.05%
Debt term	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	398,159	519,115
Asset-Backed Notes | Oportun Funding XIV, LLC (Series 2021-A)
Debt Instrument [Line Items]
Original Balance	375,000	375,000
Current balance	$ 78,684	$ 182,164
Weighted average interest rate (as a percent)	1.79%	1.78%
Debt term	2 years	2 years
Asset-Backed Notes | Oportun Funding XIV, LLC (Series 2021-A) | Initial Collateral
Debt Instrument [Line Items]
Collateral balance	$ 383,632	$ 383,632
Asset-Backed Notes | Oportun Funding XIV, LLC (Series 2021-A) | Current Collateral
Debt Instrument [Line Items]
Collateral balance	$ 89,564	200,758
Asset-Backed Notes | Oportun Funding XIII, LLC (Series 2019-A)
Debt Instrument [Line Items]
Original Balance		279,412
Current balance		$ 0
Weighted average interest rate (as a percent)		0.00%
Debt term		3 years
Asset-Backed Notes | Oportun Funding XIII, LLC (Series 2019-A) | Initial Collateral
Debt Instrument [Line Items]
Collateral balance		$ 294,118
Asset-Backed Notes | Oportun Funding XIII, LLC (Series 2019-A) | Current Collateral
Debt Instrument [Line Items]
Collateral balance		$ 0