Borrower Loans and Notes, at Fair Value - Schedule of Fair Value of Borrower Loans and Notes (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2026	Dec. 31, 2025
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Borrower Loans, at Fair value	$ 215,711	$ 309,737
Notes, at Fair value	212,396	243,900
Prosper Funding LLC
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Borrower Loans, at Fair value	215,711	245,337
Notes, at Fair value	212,396	243,900
Notes
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Notes, Aggregate principal balance and interest outstanding	225,184	256,929
Notes, Fair value adjustments	(12,788)	(13,029)
Notes, at Fair value	212,396	243,900
Notes \| Prosper Funding LLC
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Notes, Aggregate principal balance and interest outstanding	225,184	256,929
Notes, Fair value adjustments	(12,788)	(13,029)
Notes, at Fair value	212,396	243,900
Borrower Loans
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Borrower Loans, Aggregate principal balance and interest outstanding	227,393	324,505
Borrower Loans, Fair value adjustment	(11,682)	(14,768)
Borrower Loans, at Fair value	215,711	309,737
Borrower Loans \| Prosper Funding LLC
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Borrower Loans, Aggregate principal balance and interest outstanding	227,393	255,132
Borrower Loans, Fair value adjustment	(11,682)	(9,795)
Borrower Loans, at Fair value	$ 215,711	$ 245,337

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