v3.3.1.900
Stockholders' Equity of the Company (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
Sep. 30, 2015
Jul. 01, 2015
Jun. 30, 2015
Class of Stock [Line Items]                        
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period             212,468          
Aggregate net proceeds after sales agent compensation           $ 249,600            
Aggregate gross proceeds             $ 387,398 $ 102,229 $ 349,951      
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  
purchase price, value of shares issued to acquire land             $ 0 $ 21,631 $ 0      
Share Repurchase, remaining number of shares authorized to be repurchased           988,025 988,025          
Series G Cumulative Redeemable Preferred Stock                        
Class of Stock [Line Items]                        
Preferred stock, dividend rate         6.875%   6.875%   6.875%      
Preferred stock (in shares)           4,000,000 4,000,000 4,000,000        
Series H Cumulative Redeemable Preferred Stock                        
Class of Stock [Line Items]                        
Preferred stock, dividend rate       6.375%     6.375%   6.375%      
Preferred stock (in shares)           4,000,000 4,000,000 4,000,000        
Common Stock                        
Class of Stock [Line Items]                        
Common stock, shares issued                 86,259,684     92,258,690
December 2014 At-The-Market Program [Member]                        
Class of Stock [Line Items]                        
At Market Stock Offering Program Aggregate Value Of Common Stock             $ 300,000          
Issuance of Equity under ATM Program [Member] | Common Stock                        
Class of Stock [Line Items]                        
Share of common stock sold during the period             1,866,267 1,599,123 1,040,838      
Aggregate net proceeds after sales agent compensation             $ 138,200 $ 103,100 $ 54,400      
Aggregate gross proceeds             140,100 $ 104,700 $ 55,300      
At Market Stock Offering Program Aggregate Value Of Common Stock             $ 200,000          
Issuance of Equity - equity offering [Domain] | Common Stock                        
Class of Stock [Line Items]                        
Share of common stock sold during the period     6,175,000                  
Market Measure-Based Restricted Stock Units (RSUs) [Member]                        
Class of Stock [Line Items]                        
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period             127,657 119,098        
Time-Based Restricted Stock Units (RSUs) [Member]                        
Class of Stock [Line Items]                        
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period             84,811 117,506        
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]
Issuance of Equity under ATM Program [Member] | Common Stock                        
Class of Stock [Line Items]                        
At Market Stock Aggregate Gross Sales Price of Common Stock                   $ 150,100    
Issuance of Equity - equity offering [Domain] | Issuance of Equity - equity offering [Domain] | Common Stock                        
Class of Stock [Line Items]                        
Aggregate gross proceeds $ 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.