v3.26.3
Convertible Preferred Stock, Convertible Preferred Stock Warrant Liability and Common Stock - Additional Information (Details)
$ / shares in Units, $ in Thousands
 3 Months Ended 9 Months Ended
Jun. 30, 2026
shares
Jun. 15, 2026
USD ($)
shares
May 15, 2026
USD ($)
shares
May 05, 2026
shares
Apr. 26, 2026
shares
Mar. 31, 2026
USD ($)
$ / shares
shares
Mar. 19, 2026
USD ($)
shares
Jul. 30, 2025
USD ($)
shares
Jul. 21, 2020
shares
Dec. 23, 2019
shares
Feb. 27, 2017
$ / shares
shares
Feb. 16, 2016
Sep. 30, 2026
USD ($)
$ / shares
shares
Jun. 30, 2026
shares
Sep. 30, 2025
USD ($)
shares
Sep. 30, 2026
USD ($)
time
$ / shares
shares
Sep. 30, 2025
USD ($)
shares
Dec. 31, 2025
vote
$ / shares
shares
Jun. 30, 2025
shares
Mar. 31, 2025
shares
Dec. 31, 2024
shares
Sep. 20, 2017
$ / shares
shares
Dec. 16, 2016
shares
Class of Stock [Line Items]                                              
Purchase of stock by consolidated VIE (in shares) 244,130                                            
Proceeds from exercises of series e-1 and series f convertible preferred stock warrants | $                               $ 1,611 $ 516            
Aggregate fair value of warrants | $                               $ (58,056) $ 37,254            
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       625,000,000  
Common stock, par value (in dollars per share) | $ / shares                         $ 0.01     $ 0.01   $ 0.01       $ 0.01  
Convertible preferred stock, authorized (in shares)                         444,760,848     444,760,848   444,760,848       444,760,848  
Preferred stock, par value (in dollars per share) | $ / shares                                           $ 0.01  
Common stock, issued (in shares)                         81,116,014     81,116,014   79,138,710          
Common stock, outstanding (in shares)                         79,935,949     79,935,949   78,202,775          
Number of votes per share | vote                                   1          
Common stock transferred (in shares) 244,130                                            
Cashless exercise of common stock warrants (in shares)         503,821                                    
Common Stock                                              
Class of Stock [Line Items]                                              
Stock split conversion ratio                       5                      
Common stock, outstanding (in shares) 84,869,054         83,476,590             84,869,054 84,869,054 83,365,510 84,869,054 83,365,510 83,380,010 82,960,790 82,769,890 82,642,684    
Exercise of stock options (in shares)                               1,229,353              
Cash proceeds | $                               $ 33              
Cashless exercise of common stock warrants (in shares)                           503,821   503,821              
Series A                                              
Class of Stock [Line Items]                                              
Purchase of convertible preferred stock by consolidated VIE Prosper Grantor Trust (in shares) 55,395                                            
Conversion ratio                         1     1              
Times the original issue | time                               3              
Liquidation preference (in dollars per share) | $ / shares                         $ 0.29     $ 0.29              
Convertible preferred stock, authorized (in shares)                         68,558,220     68,558,220              
Series B                                              
Class of Stock [Line Items]                                              
IPO value (at least) | $                               $ 2,000,000              
Aggregate proceeds (at least) | $                               $ 100,000              
Voting power (at least) (as a percent)                               60.00%              
Liquidation preference (in dollars per share) | $ / shares                         $ 0.60     $ 0.60              
Convertible preferred stock, authorized (in shares)                         35,775,880     35,775,880              
Series A-1                                              
Class of Stock [Line Items]                                              
Purchase of convertible preferred stock by consolidated VIE Prosper Grantor Trust (in shares) 58,165                                            
Voting power (at least) (as a percent)                               14.00%              
Conversion ratio                         1,000,000     1,000,000              
Liquidation preference (in dollars per share) | $ / shares                         $ 2.00     $ 2.00              
Convertible preferred stock, authorized (in shares)                         24,760,915     24,760,915              
Series D                                              
Class of Stock [Line Items]                                              
Voting power (at least) (as a percent)                               60.00%              
Liquidation preference (in dollars per share) | $ / shares                         $ 6.91     $ 6.91              
Series E-1 And Series E-2 Convertible Preferred Stock                                              
Class of Stock [Line Items]                                              
Voting power (at least) (as a percent)                               60.00%              
Series F convertible preferred stock warrants                                              
Class of Stock [Line Items]                                              
Voting power (at least) (as a percent)                               60.00%              
Preferred stock, liquidation preference, conversion basis                               0.6667              
Preferred stock, liquidation preference, conversion basis, after payment                               0.3333              
Liquidation preference (in dollars per share) | $ / shares                         $ 0.84     $ 0.84              
Exercise of warrant (in shares)   41,833,904 41,833,904       41,833,904 51,614,124     177,720,706                        
Exercise price (in dollars per share) | $ / shares                     $ 0.01                        
Aggregate fair value of warrants | $   $ 47,700 $ 42,700       $ 42,300 $ 73,300                              
Warrant expiration period (in years)                     10 years                        
Proceeds from issuance of convertible preferred stock | $   $ 400 $ 400       $ 400 $ 500                              
Class of warrant or right, outstanding (in shares)                         604,868     604,868              
Change in fair value | $                         $ 48   $ (30,500) $ 44,500 $ (32,300)            
Convertible preferred stock, authorized (in shares)                         177,720,707     177,720,707              
Series G                                              
Class of Stock [Line Items]                                              
Voting power (at least) (as a percent)                               60.00%              
Conversion ratio                         1.36     1.36              
Liquidation preference (in dollars per share) | $ / shares                         $ 1.34     $ 1.34              
Convertible preferred stock, authorized (in shares)                         37,249,497     37,249,497              
Series C                                              
Class of Stock [Line Items]                                              
Liquidation preference (in dollars per share) | $ / shares                         $ 2.87     $ 2.87              
Convertible preferred stock, authorized (in shares)                         24,404,770     24,404,770              
Series E-1                                              
Class of Stock [Line Items]                                              
Liquidation preference (in dollars per share) | $ / shares                         $ 0.84     $ 0.84              
Exercise of warrant (in shares)                     15,277,006                        
Warrant or right, exercised, fair value | $           $ 38,700                                  
Convertible preferred stock, authorized (in shares)                         35,544,141     35,544,141              
Series E-2                                              
Class of Stock [Line Items]                                              
Preferred stock, liquidation preference, conversion basis                               0.6667              
Preferred stock, liquidation preference, conversion basis, after payment                               0.3333              
Liquidation preference (in dollars per share) | $ / shares                         $ 0.84     $ 0.84              
Convertible preferred stock, authorized (in shares)                         16,858,078     16,858,078              
Series E-1 Warrants                                              
Class of Stock [Line Items]                                              
Exercise of warrant (in shares)           35,544,141                                 20,267,135
Exercise price (in dollars per share) | $ / shares           $ 0.01                                  
Proceeds from exercises of series e-1 and series f convertible preferred stock warrants | $           $ 400                                  
Aggregate fair value of warrants | $                             $ 4,600 $ 13,500 $ 5,000            
Common Stock                                              
Class of Stock [Line Items]                                              
Purchase of stock by consolidated VIE (in shares)                   2,196,665                          
Convertible Preferred Stock Held by Consolidated VIE | Series A                                              
Class of Stock [Line Items]                                              
Purchase of convertible preferred stock by consolidated VIE Prosper Grantor Trust (in shares)                 34,670,420                            
Return of convertible preferred stock (in shares)       289,560                                      
Convertible Preferred Stock Held by Consolidated VIE | Series B                                              
Class of Stock [Line Items]                                              
Purchase of convertible preferred stock by consolidated VIE Prosper Grantor Trust (in shares)                 16,577,495