v3.26.1
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Additional Information (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Sep. 30, 2024
Mar. 31, 2024
Entity Information [Line Items]          
Administration agreement license, fixed monthly fee $ 0.3        
Servicing fee, percent 1.00%        
Fee deposits, percentage 0.05        
Advertising costs $ 17.8 $ 13.7 $ 17.6    
Borrower Loans          
Entity Information [Line Items]          
Servicing fee, percent 1.00%        
Loan trailing fee, percent 0.075%        
Prosper Funding LLC          
Entity Information [Line Items]          
Servicing fee, percent 1.00%        
Fee deposits, percentage 0.05        
Prosper Funding LLC | Borrower Loans          
Entity Information [Line Items]          
Servicing fee, percent 1.00%        
Loan trailing fee, percent 0.075%        
Coastal Allocations | Borrower Loans          
Entity Information [Line Items]          
Servicing fee, percent 1.00%        
Minimum          
Entity Information [Line Items]          
Transaction fee percentage 1.00%        
Minimum | Internal-use software and website development costs          
Entity Information [Line Items]          
Property and equipment, estimated useful life 1 year        
Minimum | Prosper Funding LLC | Internal-use software and website development costs          
Entity Information [Line Items]          
Property and equipment, estimated useful life 1 year        
Maximum          
Entity Information [Line Items]          
Transaction fee percentage 9.99%        
Maximum | Internal-use software and website development costs          
Entity Information [Line Items]          
Property and equipment, estimated useful life 5 years        
Maximum | Prosper Funding LLC | Internal-use software and website development costs          
Entity Information [Line Items]          
Property and equipment, estimated useful life 5 years        
Credit Card Program Agreement          
Entity Information [Line Items]          
Outstanding credit card principal balance $ 375.0   $ 300.0 $ 375.0 $ 350.0
Prosper Allocations | Credit Card Program Agreement          
Entity Information [Line Items]          
Revised allocation of customer accounts     90.00%   95.00%
Coastal Allocations | Credit Card Program Agreement          
Entity Information [Line Items]          
Revised allocation of customer accounts 0.75%   10.00%   5.00%
Coastal Allocations | Credit Card Program Agreement | Minimum          
Entity Information [Line Items]          
Revised allocation of customer accounts 0.00%        
Coastal Allocations | Credit Card Program Agreement | Maximum          
Entity Information [Line Items]          
Revised allocation of customer accounts 5.00%