v3.26.3
Debt Obligations - Schedule of Debt (Details) - USD ($)
 9 Months Ended
Sep. 30, 2026
Dec. 31, 2025
Debt Instrument [Line Items]    
Outstanding Principal $ 2,405,602,000  
Unamortized debt issuance costs (4,929,000) $ (5,887,000)
Unamortized debt issuance costs $ 4,929,000 5,887,000
Minimum    
Debt Instrument [Line Items]    
Weighted average life (years) 1 year 3 months 18 days  
Maximum    
Debt Instrument [Line Items]    
Weighted average life (years) 1 year 9 months 18 days  
Secured financing agreements, net    
Debt Instrument [Line Items]    
Maximum Facility Size $ 4,819,124,000  
Outstanding Principal 2,405,602,000  
Carrying Value $ 2,397,405,000  
Weighted Average Funding Cost 5.70%  
Secured financing agreements, net | Commercial Real Estate Loans    
Debt Instrument [Line Items]    
Unamortized debt issuance costs $ (8,200,000) (8,400,000)
Unamortized debt issuance costs 8,200,000 8,400,000
Secured Financing Agreements | Secured financing agreements, net    
Debt Instrument [Line Items]    
Carrying Value 2,397,405,000 2,862,689,000
Secured Financing Agreements | KREF Lending XV | Secured financing agreements, net    
Debt Instrument [Line Items]    
Maximum Facility Size 300,000,000  
Outstanding Principal 175,360,000  
Carrying Value $ 174,761,000 237,422,000
Weighted Average Funding Cost 5.60%  
Outstanding Principal $ 219,200,000  
Carrying Value 216,452,000  
Secured Financing Agreements | KREF Lending XVI | Secured financing agreements, net    
Debt Instrument [Line Items]    
Maximum Facility Size 187,125,000  
Outstanding Principal 172,463,000  
Carrying Value $ 171,070,000 99,083,000
Weighted Average Funding Cost 5.80%  
Outstanding Principal $ 219,200,000  
Carrying Value 215,550,000  
Secured Financing Agreements | KREF Lending XVII | Secured financing agreements, net    
Debt Instrument [Line Items]    
Maximum Facility Size 250,000,000  
Outstanding Principal 161,542,000  
Carrying Value $ 160,239,000 89,178,000
Weighted Average Funding Cost 5.60%  
Outstanding Principal $ 206,342,000  
Carrying Value 202,305,000  
Secured Financing Agreements | KREF Lending XIX - GBP | Secured financing agreements, net    
Debt Instrument [Line Items]    
Maximum Facility Size 130,682,000  
Outstanding Principal 126,234,000  
Carrying Value $ 125,433,000 0
Weighted Average Funding Cost 5.40%  
Outstanding Principal $ 174,116,000  
Carrying Value 171,052,000  
Secured Financing Agreements | BMO Facility | Secured financing agreements, net    
Debt Instrument [Line Items]    
Maximum Facility Size 300,000,000  
Outstanding Principal 71,126,000  
Carrying Value $ 71,096,000 71,063,000
Weighted Average Funding Cost 5.70%  
Outstanding Principal $ 90,795,000  
Carrying Value 90,165,000  
Secured Financing Agreements | KREF Lending IX | Secured financing agreements, net    
Debt Instrument [Line Items]    
Maximum Facility Size 0  
Outstanding Principal 0  
Carrying Value $ 0 271,455,000
Weighted Average Funding Cost 0.00%  
Outstanding Principal $ 0  
Carrying Value 0  
Secured Financing Agreements | HSBC Facility | Secured financing agreements, net    
Debt Instrument [Line Items]    
Maximum Facility Size 250,000,000  
Outstanding Principal 0  
Carrying Value $ 0 0
Weighted Average Funding Cost 0.00%  
Outstanding Principal $ 0  
Carrying Value 0  
Secured Financing Agreements | KREF Lending XX - EUR | Secured financing agreements, net    
Debt Instrument [Line Items]    
Maximum Facility Size 128,322,000  
Outstanding Principal 111,661,000  
Carrying Value $ 110,411,000 0
Weighted Average Funding Cost 5.00%  
Outstanding Principal $ 131,421,000  
Carrying Value 128,813,000  
Secured Financing Agreements | KREF Lending XIV | Secured financing agreements, net    
Debt Instrument [Line Items]    
Maximum Facility Size 125,000,000  
Outstanding Principal 83,955,000  
Carrying Value $ 83,947,000 79,780,000
Weighted Average Funding Cost 6.70%  
Outstanding Principal $ 113,552,000  
Carrying Value 112,845,000  
Secured Financing Agreements | KREF Lending XIII | Secured financing agreements, net    
Debt Instrument [Line Items]    
Maximum Facility Size 0  
Outstanding Principal 0  
Carrying Value $ 0 194,678,000
Weighted Average Funding Cost 0.00%  
Outstanding Principal $ 0  
Carrying Value 0  
Secured Financing Agreements | KREF Lending XI | Secured financing agreements, net    
Debt Instrument [Line Items]    
Maximum Facility Size 0  
Outstanding Principal 0  
Carrying Value $ 0 90,000,000
Weighted Average Funding Cost 0.00%  
Outstanding Principal $ 0  
Carrying Value 0  
Secured Financing Agreements | Wells Fargo | Secured financing agreements, net    
Debt Instrument [Line Items]    
Maximum Facility Size 600,000,000  
Outstanding Principal 375,453,000  
Carrying Value $ 375,119,000 578,569,000
Weighted Average Funding Cost 5.60%  
Outstanding Principal $ 560,656,000  
Carrying Value 558,730,000  
Secured Financing Agreements | Morgan Stanley | Secured financing agreements, net    
Debt Instrument [Line Items]    
Maximum Facility Size 300,000,000  
Outstanding Principal 252,171,000  
Carrying Value $ 251,526,000 308,388,000
Weighted Average Funding Cost 6.20%  
Outstanding Principal $ 486,473,000  
Carrying Value 445,619,000  
Secured Financing Agreements | Morgan Stanley - GBP/EUR | Secured financing agreements, net    
Debt Instrument [Line Items]    
Maximum Facility Size 397,995,000  
Outstanding Principal 159,653,000  
Carrying Value $ 158,737,000 160,725,000
Weighted Average Funding Cost 4.90%  
Outstanding Principal $ 212,870,000  
Carrying Value 209,396,000  
Secured Financing Agreements | Goldman Sachs | Secured financing agreements, net    
Debt Instrument [Line Items]    
Maximum Facility Size 150,000,000  
Outstanding Principal 0  
Carrying Value   169,451,000
Unamortized debt issuance costs $ (365,000)  
Weighted Average Funding Cost 0.00%  
Outstanding Principal $ 30,600,000  
Carrying Value 30,600,000  
Unamortized debt issuance costs 365,000  
Term Loan Facility | KREF Lending VII | Secured financing agreements, net    
Debt Instrument [Line Items]    
Maximum Facility Size 1,000,000,000  
Outstanding Principal 615,984,000  
Carrying Value $ 615,431,000 512,897,000
Weighted Average Funding Cost 5.90%  
Outstanding Principal $ 774,692,000  
Carrying Value $ 770,583,000  
Weighted average life (years) 5 years  
Extension term 2 years  
Revolving Credit Agreement | Secured financing agreements, net    
Debt Instrument [Line Items]    
Maximum Facility Size $ 700,000,000  
Outstanding Principal 100,000,000  
Carrying Value $ 100,000,000 $ 0
Weighted Average Funding Cost 6.10%  
Deferred financing/debt issuance costs $ 4,900,000