v3.25.4
Secured and Unsecured Debt of the Operating Partnership - Secured Debt and Additional Information (Details)
 1 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2025
USD ($)
Sep. 30, 2024
USD ($)
Sep. 30, 2025
Dec. 31, 2025
USD ($)
debt_covenant
Dec. 31, 2024
USD ($)
Dec. 31, 2023
USD ($)
Aug. 31, 2025
USD ($)
Mar. 31, 2024
USD ($)
Jan. 31, 2024
USD ($)
Debt Instrument [Line Items]                  
Repayments of unsecured debt       $ 400,000,000 $ 723,712,000 $ 0      
Kilroy Realty L.P.                  
Debt Instrument [Line Items]                  
Long-term debt, gross       4,625,442,000          
Less: Unamortized Net Discounts and Deferred Financing costs       35,983,000          
Repayments of unsecured debt       $ 400,000,000 723,712,000 $ 0      
Number of noncompliant debt covenants that could require immediate repayment of full principal balance of associated debt | debt_covenant       1          
Secured debt | Kilroy Realty L.P.                  
Debt Instrument [Line Items]                  
Net book value of properties pledged as collateral for secured debt       $ 950,400,000          
Unsecured debt | Kilroy Realty L.P.                  
Debt Instrument [Line Items]                  
Long-term debt, gross       3,825,000,000 3,825,000,000        
Less: Unamortized Net Discounts and Deferred Financing costs       27,949,000 24,205,000        
Unsecured debt | Kilroy Realty L.P. | 6.250% Unsecured Senior Notes                  
Debt Instrument [Line Items]                  
Principal amount of debt                 $ 400,000,000
Long-term debt, gross       $ 400,000,000 400,000,000       400,000,000.0
Unamortized discount (premium), net                 $ 4,500,000
Stated Coupon Rate       6.25%         6.25%
Unsecured debt | Kilroy Realty L.P. | 3.450% Unsecured Senior Notes Due 2024                  
Debt Instrument [Line Items]                  
Principal amount of debt         425,000,000        
Long-term debt, gross         $ 403,700,000        
Stated Coupon Rate         3.45%        
Unsecured debt | Kilroy Realty L.P. | 3.450% Unsecured Senior Notes Due December 15, 2024                  
Debt Instrument [Line Items]                  
Principal amount of debt         $ 425,000,000        
Unsecured debt | Kilroy Realty L.P. | 5.875% Unsecured Senior Notes Due 2035                  
Debt Instrument [Line Items]                  
Long-term debt, gross       $ 400,000,000 0   $ 400,000,000    
Stated Coupon Rate       5.875%     5.875%    
Less: Unamortized Net Discounts and Deferred Financing costs             $ 4,000,000    
Unsecured debt | Kilroy Realty L.P. | 4.375% Unsecured Senior Notes Due 2036                  
Debt Instrument [Line Items]                  
Stated Coupon Rate 4.375%   4.375%            
Extinguishment of debt, amount $ 400,000,000                
Revolving credit facility | Kilroy Realty L.P.                  
Debt Instrument [Line Items]                  
Line of credit facility, maximum borrowing capacity       $ 1,100,000,000 $ 1,100,000,000        
Revolving credit facility | Kilroy Realty L.P. | $400.0 million term loan facility                  
Debt Instrument [Line Items]                  
Line of credit facility, maximum borrowing capacity               $ 1,100,000,000  
Term Loan Facility | Kilroy Realty L.P. | $400.0 million term loan facility                  
Debt Instrument [Line Items]                  
Line of credit facility, maximum borrowing capacity               $ 520,000,000  
Repayments of unsecured debt   $ 120,000,000   200,000,000          
Term Loan Facility | Kilroy Realty L.P. | Unsecured New Term Loan Facility                  
Debt Instrument [Line Items]                  
Principal amount of debt       $ 200,000,000          
Maturity period     12 months 12 months