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Transactions With Related Parties - Affiliate Transactions (Details) $ in Thousands, € in Millions, £ in Millions | 3 Months Ended | 9 Months Ended |  |  |  |  |
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Sep. 30, 2025 USD ($) loan | Jun. 30, 2025 USD ($) loan | Dec. 31, 2024 USD ($) loan | Sep. 30, 2024 USD ($) | Sep. 30, 2024 EUR (€) | Sep. 30, 2024 GBP (£) | Sep. 30, 2025 USD ($) loan | Sep. 30, 2024 USD ($) | Mar. 31, 2025 USD ($) | Sep. 30, 2024 EUR (€) | Sep. 30, 2024 GBP (£) | Dec. 31, 2021 EUR (€) | Dec. 31, 2019 EUR (€) | Dec. 31, 2018 GBP (£)
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total face value | $ 13,037,822 |  |  |  |  |  | $ 13,037,822 |  |  |  |  |  |  |
Investment in unconsolidated entities |  |  |  |  |  |  | 178,664 | $ 0 |  |  |  |  |  |
Origination and other fees received on loans receivable |  |  |  |  |  |  | 46,882 | 26,140 |  |  |  |  |  |
Book Value | $ 182,598 | $ 108,087 | $ 4,452 |  |  |  | 182,598 |  |  |  |  |  |  |
Repayment of loan participations |  |  |  |  |  |  | $ 104,028 | 235,960 |  |  |  |  |  |
Bank Loan Portfolio Joint Venture |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership percentage | 35.00% |  |  |  |  |  | 35.00% |  |  |  |  |  |  |
Book Value | $ 104,867 | 55,906 | $ 0 |  |  |  | $ 104,867 |  |  |  |  |  |  |
Bank Loan Portfolio Joint Venture 1 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Investment in unconsolidated entities |  | $ 57,600 |  |  |  |  |  |  |  |  |  |  |  |
Ownership percentage |  | 29.00% |  |  |  |  |  |  |  |  |  |  |  |
Bank Loan Portfolio Joint Venture 2 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Investment in unconsolidated entities | $ 44,700 |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership percentage | 50.00% |  |  |  |  |  | 50.00% |  |  |  |  |  |  |
Net Lease Joint Venture |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership percentage | 75.00% |  | 75.00% |  |  |  | 75.00% |  |  |  |  |  |  |
Book Value | $ 77,731 | $ 52,181 | $ 4,452 |  |  |  | $ 77,731 |  |  |  |  |  |  |
Secured term loans, net |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total face value | 1,808,127 |  | 1,764,437 |  |  |  | 1,808,127 |  |  |  |  |  |  |
Senior secured notes, net |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total face value | 785,316 |  | 785,316 |  |  |  | 785,316 |  |  |  |  |  |  |
Securitized debt obligations, net |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Face Value | 2,479,417 |  | 1,936,967 |  |  |  | 2,479,417 |  |  |  |  |  |  |
Principal Balance, collateral assets | 3,098,228 |  | 2,552,403 |  |  |  | 3,098,228 |  |  |  |  |  |  |
Total face value | 2,479,417 |  | 1,936,967 |  |  |  | 2,479,417 |  |  |  |  |  |  |
B-6 Term Loan | Secured term loans, net |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maximum borrowing capacity | 1,000,000 | 1,000,000 |  |  |  |  | 1,000,000 |  |  |  |  |  |  |
Total face value | 1,045,754 |  | 0 |  |  |  | 1,045,754 |  |  |  |  |  |  |
B-5 Term Loan | Secured term loans, net |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maximum borrowing capacity |  |  | 650,000 |  |  |  |  |  |  |  |  |  |  |
Total face value | 0 |  | 650,000 |  |  |  | 0 |  |  |  |  |  |  |
December 2024 | Senior secured notes, net |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Face Value |  |  | 450,000 |  |  |  |  |  |  |  |  |  |  |
Total face value | 450,000 |  | 450,000 |  |  |  | 450,000 |  |  |  |  |  |  |
2025 FL5 Underlying Collateral Assets | Securitized debt obligations, net |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Principal Balance, collateral assets | 898,950 |  |  |  |  |  | 898,950 |  | $ 1,000,000 |  |  |  |  |
B-7 Term Loan | Secured term loans, net |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maximum borrowing capacity | 453,100 |  |  |  |  |  | 453,100 |  |  |  |  |  |  |
Total face value | 453,105 |  | $ 0 |  |  |  | 453,105 |  |  |  |  |  |  |
Related Party |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Face amount of loans | $ 606,000 | $ 1,400,000 |  | $ 94,400 |  |  | 606,000 | 94,400 |  |  | £ 303.5 | € 350.0 | € 350.0 | £ 148.7
Related party transaction, interest in loan, percentage |  |  |  | 17.00% | 17.00% | 17.00% |  |  |  |  |  |  |  |
Selling loan amount | € |  |  |  |  | € 232.0 |  |  |  |  |  |  |  |  |
Remaining loan amount in new lenders | € |  |  |  |  |  |  |  |  |  | € 347.0 |  |  |  |
Repayment of loan participations |  |  |  | $ 46,400 |  |  |  |  |  |  |  |  |  |
Related Party | Senior Participations |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proceeds of loan participations | £ |  |  |  |  |  | £ 100.0 |  |  |  |  |  |  |  |
Related Party | Senior Loans |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Face amount of loans |  |  |  | $ 560,000 |  |  |  | 560,000 |  |  |  |  |  |
Agency Multifamily Lending Partnership | Related Party |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of loans referred | loan |  |  | 3 |  |  |  |  |  |  |  |  |  |  |
Origination and other fees received on loans receivable |  |  | $ 217 |  |  |  |  |  |  |  |  |  |  |
Blackstone-Advised Investment Vehicles, or the Funds |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from sale of assets |  |  |  |  |  |  |  | 59,000 |  |  |  |  |  |
Blackstone-Advised Investment Vehicles, or the Funds | Senior Loans, Blackstone-Advised Investment Vehicle |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of loans modified | loan |  | 2 |  |  |  |  |  |  |  |  |  |  |  |
Blackstone-Advised Investment Vehicles, or the Funds | Performing Loans, Blackstone-Advised Investment Vehicle |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Origination and other fees received on loans receivable |  |  |  |  |  |  | $ 554,400 | $ 98,600 |  |  |  |  |  |
Number of loans count | loan | 4 |  |  |  |  |  | 4 |  |  |  |  |  |  |
Blackstone-Advised Investment Vehicles, or the Funds | Performing Loan |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Origination and other fees received on loans receivable |  |  |  |  |  |  | $ 148,800 |  |  |  |  |  |  |
Blackstone-Advised Investment Vehicles, or the Funds | Related Party | Senior Loans |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Face Value | $ 666,500 |  |  |  |  |  | $ 666,500 |  |  |  |  |  |  |
Count, financing provided | loan |  |  |  |  |  |  | 5 |  |  |  |  |  |  |
Blackstone-Advised Investment Vehicles, or the Funds | Related Party | Mezzanine Loan |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Face Value | 123,600 |  |  |  |  |  | $ 123,600 |  |  |  |  |  |  |
Count, financing provided | loan |  |  |  |  |  |  | 4 |  |  |  |  |  |  |
Blackstone-Advised Investment Vehicles, or the Funds | Related Party | B-6 Term Loan | Secured term loans, net |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Principal Balance, collateral assets |  | $ 83,900 |  |  |  |  |  |  |  |  |  |  |  |
Blackstone-Advised Investment Vehicles, or the Funds | Related Party | B-5 Term Loan | Secured term loans, net |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Principal Balance, collateral assets |  |  | 62,500 |  |  |  |  |  |  |  |  |  |  |
Blackstone-Advised Investment Vehicles, or the Funds | Related Party | December 2024 | Senior secured notes, net |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Principal Balance, collateral assets |  |  | $ 80,000 |  |  |  |  |  |  |  |  |  |  |
Blackstone-Advised Investment Vehicles, or the Funds | Related Party | 2025 FL5 Underlying Collateral Assets | Securitized debt obligations, net |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Principal Balance, collateral assets |  |  |  |  |  |  |  |  | $ 75,000 |  |  |  |  |
Blackstone-Advised Investment Vehicles, or the Funds | Related Party | B-7 Term Loan | Secured term loans, net |  |  |  |  |  |  |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Principal Balance, collateral assets | $ 33,000 |  |  |  |  |  | $ 33,000 |  |  |  |  |  |  |

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