v3.26.1
CONVERTIBLE PREFERRED STOCK, CONVERTIBLE PREFERRED STOCK WARRANT LIABILITY AND COMMON STOCK - Additional Information (Details)
 1 Months Ended 12 Months Ended
Jul. 29, 2025
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Jul. 21, 2020
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Dec. 23, 2019
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Sep. 20, 2017
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Feb. 27, 2017
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Nov. 17, 2016
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Feb. 16, 2016
Jul. 16, 2014
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Jun. 18, 2014
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Apr. 30, 2015
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May 31, 2014
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Sep. 30, 2013
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Jan. 31, 2013
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Dec. 31, 2025
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time
vote
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Dec. 31, 2024
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Dec. 31, 2023
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Dec. 31, 2022
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Dec. 31, 2016
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Dec. 16, 2016
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Class of Stock [Line Items]                                      
Stock split conversion ratio                         1            
Common stock convertible ratio if preferred stock did not participate                         10            
Convertible preferred stock, authorized (in shares)                           444,760,848 444,760,848        
Shares authorized to be repurchased (in shares)     7,221,020                                
Dividends | $                           $ 0          
Aggregate fair value of warrants | $                           $ 42,103,000 $ 46,208,000 $ 48,695,000      
Common and preferred stock, shares authorized (in shares)       1,069,760,848                              
Common stock, authorized (in shares)       625,000,000                   625,000,000 625,000,000        
Common stock, par value (in dollars per share) | $ / shares       $ 0.01                   $ 0.01 $ 0.01        
Preferred stock, shares authorized                           444,760,848          
Preferred stock, par value (in dollars per share) | $ / shares       $ 0.01                              
Common stock, issued (in shares)                           79,138,710 78,401,384        
Common stock, outstanding (in shares)                           78,202,775 77,465,449        
Voting rights per share | vote                           1          
Common Stock                                      
Class of Stock [Line Items]                                      
Stock split conversion ratio             5                        
Common stock, outstanding (in shares)                           83,380,010 82,642,684 82,102,629 79,465,150    
Exercise of stock options (in shares)                           737,326 540,055        
Cash proceeds | $                           $ 47,000 $ 18,000        
Series F Warrant | Consortium Purchase Agreement                                      
Class of Stock [Line Items]                                      
Warrant to purchase shares (in shares)         177,720,706                            
Number of warrants issued to the Consortium (in shares)         3                            
Series A                                      
Class of Stock [Line Items]                                      
Shares issued (in shares)                         69,340,760            
Convertible preferred stock, price per share (in dollars per share) | $ / shares                         $ 0.29            
Proceeds from issuance of convertible preferred stock | $                         $ 19,800,000            
Stock issued during the period (in shares)     2,130,035         782,540                      
Convertible preferred stock, authorized (in shares)                           68,558,220          
Conversion ratio of preferred stock into prosper common stock                           1          
Times the original issue | time                           3          
Liquidation preference per share (in dollars per share) | $ / shares                           $ 0.29          
Series A | Convertible Preferred Stock Held by Consolidated VIE                                      
Class of Stock [Line Items]                                      
Repurchase of convertible preferred stock (in shares)   34,670,420                                  
Series A-1                                      
Class of Stock [Line Items]                                      
Shares issued (in shares)                         25,585,910            
Convertible preferred stock, price per share (in dollars per share) | $ / shares                         $ 0.01            
Stock split conversion ratio                         1,000,000            
Liquidation preference per share (in dollars per share) | $ / shares                         $ 2.00            
Stock issued during the period (in shares)     2,245,600                                
Convertible preferred stock, authorized (in shares)                           24,760,915          
Percentage of holders of preferred stock required to request for conversion, minimum (at least)                           14.00%          
Conversion ratio of preferred stock into prosper common stock                           1,000,000          
Liquidation preference per share (in dollars per share) | $ / shares                           $ 2.00          
Series B                                      
Class of Stock [Line Items]                                      
Shares issued (in shares)                       41,443,670              
Convertible preferred stock, price per share (in dollars per share) | $ / shares                       $ 0.60              
Proceeds from issuance of convertible preferred stock | $                       $ 24,900,000              
Stock issued during the period (in shares)     648,720         5,667,790                      
Convertible preferred stock, authorized (in shares)                           35,775,880          
Value prior to closing of underwritten initial public offering (at least) | $                           $ 2,000,000,000          
Aggregate proceeds to the entity before deducting underwriters commissions and expenses (at least) | $                           $ 100,000,000          
Percentage of holders of preferred stock required to request for conversion, minimum (at least)                           60.00%          
Liquidation preference per share (in dollars per share) | $ / shares                           $ 0.60          
Series B | Convertible Preferred Stock Held by Consolidated VIE                                      
Class of Stock [Line Items]                                      
Repurchase of convertible preferred stock (in shares)   16,577,495                                  
Series C                                      
Class of Stock [Line Items]                                      
Shares issued (in shares)                     24,404,770                
Convertible preferred stock, price per share (in dollars per share) | $ / shares                     $ 2.87                
Proceeds from issuance of convertible preferred stock | $                     $ 69,900,000                
Convertible preferred stock, authorized (in shares)                           24,404,770          
Liquidation preference per share (in dollars per share) | $ / shares                           $ 2.87          
Series A and Series B Convertible Preferred Stock                                      
Class of Stock [Line Items]                                      
Shares issued (in shares)                 6,963,785                    
Convertible preferred stock, price per share (in dollars per share) | $ / shares                 $ 2.87                    
Repurchase of preferred stock | $               $ 18,500,000                      
Series D                                      
Class of Stock [Line Items]                                      
Shares issued (in shares)                   23,888,640                  
Convertible preferred stock, price per share (in dollars per share) | $ / shares                   $ 6.91                  
Proceeds from issuance of convertible preferred stock | $                   $ 164,800,000                  
Liquidation preference per share (in dollars per share) | $ / shares                           $ 6.91          
Series E                                      
Class of Stock [Line Items]                                      
Convertible preferred stock, authorized (in shares)                                   40,000,000  
Series E-1                                      
Class of Stock [Line Items]                                      
Convertible preferred stock, authorized (in shares)                           35,544,141          
Warrant to purchase shares (in shares)         15,277,006                           20,267,135
Exercise of common stock warrants (in dollars per share) | $ / shares           $ 0.01                         $ 0.01
Liquidation preference per share (in dollars per share) | $ / shares                           $ 0.84          
Warrant expiration period           10 years                          
Change in fair value | $                           $ (6,000,000.0) (7,100,000)        
Series E-1 Warrants                                      
Class of Stock [Line Items]                                      
Warrant to purchase shares (in shares)         15,277,006                            
Series F Convertible Preferred Stock warrants                                      
Class of Stock [Line Items]                                      
Proceeds from issuance of convertible preferred stock | $ $ 500,000                                    
Convertible preferred stock, authorized (in shares)                           177,720,707          
Warrant to purchase shares (in shares) 51,614,124       177,720,706                            
Exercise of common stock warrants (in dollars per share) | $ / shares         $ 0.01                            
Percentage of holders of preferred stock required to request for conversion, minimum (at least)                           60.00%          
Percent of liquidation preference                           66.60%          
Liquidation rights after payment or payment set aside, percent of liquidation preference                           33.30%          
Liquidation preference per share (in dollars per share) | $ / shares                           $ 0.84          
Change in fair value | $                           $ (36,100,000) $ (39,100,000)        
Class of warrant or right expiration period         10 years                            
Aggregate fair value of warrants | $ $ 73,300,000                                    
Fair value, liability, recurring basis, unobservable input reconciliation, gain (loss), statement of income or comprehensive income [Extensible Enumeration]                           Change in Fair Value of Financial Instruments Change in Fair Value of Financial Instruments        
Series G                                      
Class of Stock [Line Items]                                      
Shares issued (in shares)       37,249,497                              
Convertible preferred stock, authorized (in shares)                           37,249,497          
Share price (in dollars per share) | $ / shares       $ 1.34                              
Proceeds net issuance cost | $       $ 47,900,000                              
Percentage of holders of preferred stock required to request for conversion, minimum (at least)                           60.00%          
Conversion ratio of preferred stock into prosper common stock                           1.36          
Liquidation preference per share (in dollars per share) | $ / shares                           $ 1.34          
Common Stock                                      
Class of Stock [Line Items]                                      
Stock issued during the period (in shares)     2,196,665                                
Series D                                      
Class of Stock [Line Items]                                      
Convertible preferred stock, authorized (in shares)                           23,888,640          
Percentage of holders of preferred stock required to request for conversion, minimum (at least)                           60.00%          
Series E-1 And Series E-2 Convertible Preferred Stock                                      
Class of Stock [Line Items]                                      
Percentage of holders of preferred stock required to request for conversion, minimum (at least)                           60.00%          
Series E-2                                      
Class of Stock [Line Items]                                      
Convertible preferred stock, authorized (in shares)                           16,858,078          
Percent of liquidation preference                           66.60%          
Liquidation rights after payment or payment set aside, percent of liquidation preference                           33.30%          
Liquidation preference per share (in dollars per share) | $ / shares                           $ 0.84