v3.3.1.900
Preferred and Common Units of the Operating Partnership (Details Textuals) - USD ($)
$ / shares in Units, $ in Thousands
 1 Months Ended 3 Months Ended 12 Months Ended
Sep. 18, 2013
Oct. 23, 2014
Sep. 30, 2013
Aug. 31, 2012
Mar. 31, 2012
Dec. 31, 2015
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Jul. 01, 2015
Jun. 30, 2015
Jan. 27, 2015
Class of Stock [Line Items]                        
Common Stock, Shares, Issued                   3,773,766    
Shares Issued, Price Per Share                   $ 66.19    
At Market Stock Aggregate Gross Sales Price of Common Stock                   $ 249,800    
Proceeds from Issuance of Common stock, net           $ 249,600            
purchase price, value of shares issued to acquire land             $ 0 $ 21,631 $ 0      
Net proceeds from issuance of common stock             $ 387,398 $ 102,229 $ 349,951      
Share price per unit of common units issued (dollars per unit)                       $ (75.34)
Series H Cumulative Redeemable Preferred Stock                        
Class of Stock [Line Items]                        
Preferred units issued                 4,000,000      
Preferred stock, dividend rate       6.375%     6.375%   6.375%      
Preferred Stock, Shares Outstanding           4,000,000 4,000,000 4,000,000        
Series H Cumulative Redeemable Preferred Stock | Series H Cumulative Redeemable Preferred Unit [Member]                        
Class of Stock [Line Items]                        
Preferred units issued                     4,000,000  
Series G Cumulative Redeemable Preferred Stock                        
Class of Stock [Line Items]                        
Preferred units issued                 4,000,000      
Preferred stock, dividend rate         6.875%   6.875%   6.875%      
Preferred Stock, Shares Outstanding           4,000,000 4,000,000 4,000,000        
Series G Cumulative Redeemable Preferred Stock | Series G Cumulative Redeemable Preferred Unit [Member]                        
Class of Stock [Line Items]                        
Preferred units issued           4,000,000 4,000,000          
Common Stock                        
Class of Stock [Line Items]                        
Common Stock, Shares, Issued                 86,259,684   92,258,690  
Kilroy Realty, L.P. [Member] | Market Measure-Based Restricted Stock Units (RSUs) [Member]                        
Class of Stock [Line Items]                        
Number of RSUs outstanding                 247,089   425,452 [1]  
Kilroy Realty, L.P. [Member] | Series H Cumulative Redeemable Preferred Unit [Member]                        
Class of Stock [Line Items]                        
Preferred units issued                 4,000,000   4,000,000  
Preferred units outstanding           4,000,000 4,000,000   4,000,000      
Preferred stock, dividend rate             6.375%   6.375%      
Kilroy Realty, L.P. [Member] | Series G Cumulative Redeemable Preferred Unit [Member]                        
Class of Stock [Line Items]                        
Preferred units issued                 4,000,000   4,000,000  
Preferred units outstanding           4,000,000 4,000,000   4,000,000      
Preferred stock, dividend rate             6.875%   6.875%      
Kilroy Realty, L.P. [Member] | Partners Capital Common Unit [Member]                        
Class of Stock [Line Items]                        
Issuance of common units, units     6,175,000           7,210,838      
Issuance of Equity - equity offering [Domain] | Common Stock                        
Class of Stock [Line Items]                        
Share of common stock sold during the period     6,175,000                  
Issuance of Equity - equity offering [Domain] | Common Stock | Issuance of Equity - equity offering [Domain]                        
Class of Stock [Line Items]                        
Net proceeds from issuance of common stock $ 295,900                      
SFFGA [Member]                        
Class of Stock [Line Items]                        
Common Stock, Shares, Issued   351,476                    
purchase price, value of shares issued to acquire land   $ 21,600                    
[1] The amount includes nonvested RSUs. Does not include the 425,452 and 247,089 market measure-based RSUs because not all the necessary performance conditions have been met as of December 31, 2015 and 2014, respectively.