Annual report pursuant to Section 13 and 15(d)

Debt (Details 4)

v3.3.1.900
Debt (Details 4)
 1 Months Ended 12 Months Ended
Dec. 17, 2015
USD ($)
Aug. 28, 2015
USD ($)
Jun. 29, 2015
USD ($)
May. 06, 2015
USD ($)
extensions
May. 14, 2014
USD ($)
Dec. 23, 2013
USD ($)
Aug. 03, 2012
USD ($)
Feb. 14, 2012
USD ($)
Sep. 01, 2011
USD ($)
Dec. 31, 2014
USD ($)
Dec. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
Dec. 31, 2013
USD ($)
Debt Instrument [Line Items]                          
Gain (loss) on early extinguishment of debt                     $ 85,275,000 $ (9,552,000) $ (27,030,000)
Term Credit Facility Effective February 2012 [Member]                          
Debt Instrument [Line Items]                          
Initial amount borrowed               $ 250,000,000          
Term Credit Facility Effective August 2012 [Member]                          
Debt Instrument [Line Items]                          
Initial amount borrowed             $ 120,000,000            
Additional borrowing capacity available provided there is no default under the agreement             $ 80,000,000            
Term Credit Facility Effective September 2011 [Member]                          
Debt Instrument [Line Items]                          
Initial amount borrowed                 $ 400,000,000        
Repayments of debt                       100,000,000 $ 150,000,000
4.25% Exchangeable Senior Notes [Member]                          
Debt Instrument [Line Items]                          
Stated interest rate (as a percent)                         4.25%
Unamortized discount included in carrying value                   $ 3,000   $ 3,000  
Gain (loss) on early extinguishment of debt                         $ (25,900,000)
Amount of loans repaid upon entry into Revolving Credit Facility and Term Loan Agreement                         $ 239,400,000
Fixed rate mortgage loans [Member]                          
Debt Instrument [Line Items]                          
Debt settled through the surrender of real estate assets   $ 150,000,000                      
Minimum [Member] | Revolving Credit Facility [Member] | London Interbank Offered Rate (LIBOR) [Member]                          
Debt Instrument [Line Items]                          
Variable rate, spread (as a percent)                     0.875%    
Minimum [Member] | Term Credit Facility Effective February 2012 [Member] | London Interbank Offered Rate (LIBOR) [Member]                          
Debt Instrument [Line Items]                          
Variable rate, spread (as a percent)       0.90%                  
Minimum [Member] | Term Credit Facility Effective August 2012 [Member] | London Interbank Offered Rate (LIBOR) [Member]                          
Debt Instrument [Line Items]                          
Variable rate, spread (as a percent)             2.10%            
Maximum [Member] | Revolving Credit Facility [Member] | London Interbank Offered Rate (LIBOR) [Member]                          
Debt Instrument [Line Items]                          
Variable rate, spread (as a percent)                     1.60%    
Maximum [Member] | Term Credit Facility Effective February 2012 [Member] | London Interbank Offered Rate (LIBOR) [Member]                          
Debt Instrument [Line Items]                          
Variable rate, spread (as a percent)       1.85%                  
Maximum [Member] | Term Credit Facility Effective August 2012 [Member] | London Interbank Offered Rate (LIBOR) [Member]                          
Debt Instrument [Line Items]                          
Variable rate, spread (as a percent)             2.60%            
Secured Loans Due November 2015 And January 2016 [Member]                          
Debt Instrument [Line Items]                          
Gain (loss) on early extinguishment of debt                   $ (9,100,000)      
Secured Loan Due November 2015 [Member]                          
Debt Instrument [Line Items]                          
Stated interest rate (as a percent)                   5.53%   5.53%  
Amount of loans repaid upon entry into Revolving Credit Facility and Term Loan Agreement                   $ 103,000,000      
Secured Loan Due January 2016 [Member]                          
Debt Instrument [Line Items]                          
Stated interest rate (as a percent)                   5.56%   5.56%  
Amount of loans repaid upon entry into Revolving Credit Facility and Term Loan Agreement                   $ 108,500,000      
Revolving Credit Facility [Member] | Revolving Credit Facility [Member]                          
Debt Instrument [Line Items]                          
Maximum availability                     $ 800,000,000    
Expansion right, maximum borrowing capacity                     $ 1,300,000,000    
Amount available as a percentage of unencumbered Asset value                     60.00%    
Line of credit facility, extension fee percentage                     0.075%    
Remaining borrowing capacity                     $ 741,700,000    
Weighted average borrowings                     $ 125,000,000 $ 15,900,000  
Weighted average interest rate (as a percent)                   1.47% 1.40% 1.47%  
Line of Credit [Member] | Revolving Credit Facility [Member]                          
Debt Instrument [Line Items]                          
Number of extensions | extensions       2                  
Extension option period (in years)       6 months                  
Line of Credit [Member] | Revolving Credit Facility [Member] | Minimum [Member]                          
Debt Instrument [Line Items]                          
Commitment fee percentage       0.125%                  
Line of Credit [Member] | Revolving Credit Facility [Member] | Minimum [Member] | London Interbank Offered Rate (LIBOR) [Member]                          
Debt Instrument [Line Items]                          
Variable rate, spread (as a percent)       0.875%                  
Line of Credit [Member] | Revolving Credit Facility [Member] | Maximum [Member]                          
Debt Instrument [Line Items]                          
Commitment fee percentage       0.30%                  
Line of Credit [Member] | Revolving Credit Facility [Member] | Maximum [Member] | London Interbank Offered Rate (LIBOR) [Member]                          
Debt Instrument [Line Items]                          
Variable rate, spread (as a percent)       1.60%                  
Line of Credit [Member] | Term Loan Facilities [Member]                          
Debt Instrument [Line Items]                          
Maximum availability       $ 300,000,000                  
Increase to maximum borrowing capacity       200,000,000                  
Aggregate maximum borrowing capacity       $ 500,000,000                  
Unsecured Debt [Member] | Term Credit Facility Effective December 2015 [Member]                          
Debt Instrument [Line Items]                          
Maximum availability $ 250,000,000                        
Initial amount borrowed 100,000,000                        
Increase to maximum borrowing capacity $ 150,000,000                        
Unsecured Debt [Member] | Minimum [Member] | Term Credit Facility Effective December 2015 [Member] | London Interbank Offered Rate (LIBOR) [Member]                          
Debt Instrument [Line Items]                          
Variable rate, spread (as a percent) 1.40%                        
Unsecured Debt [Member] | Maximum [Member] | Term Credit Facility Effective December 2015 [Member] | London Interbank Offered Rate (LIBOR) [Member]                          
Debt Instrument [Line Items]                          
Variable rate, spread (as a percent) 2.35%                        
Senior Notes [Member]                          
Debt Instrument [Line Items]                          
Redemption price (percent)                     100.00%    
Senior Notes [Member] | 3.70% Senior Notes [Member]                          
Debt Instrument [Line Items]                          
Initial amount borrowed         $ 297,300,000                
Loan amount                     $ 300,000,000    
Stated interest rate (as a percent)         3.70%           3.70%    
Debt issuance as a percentage of principal amount         99.739%                
Unamortized discount included in carrying value                   $ 2,400,000 $ 2,100,000 $ 2,400,000  
Interest rate on debt (as a percent)                     3.85%    
Senior Notes [Member] | 3.70% Senior Notes [Member] | Adjusted Treasury [Member]                          
Debt Instrument [Line Items]                          
Basis points used in determining redemption price prior to maturity                     250.00%    
Senior Notes [Member] | 5.0% Senior Notes [Member]                          
Debt Instrument [Line Items]                          
Loan amount     $ 300,000,000                    
Stated interest rate (as a percent)     5.00%               5.00%    
Debt issuance as a percentage of principal amount     99.51%                    
Unamortized discount included in carrying value                     $ 3,300,000    
Interest rate on debt (as a percent)                     5.15%    
Proceeds from debt, net     $ 296,600,000                    
Senior Notes [Member] | 5.0% Senior Notes [Member] | Adjusted Treasury [Member]                          
Debt Instrument [Line Items]                          
Basis points used in determining redemption price prior to maturity                     450.00%    
Senior Notes [Member] | 3.60% Senior Notes [Member]                          
Debt Instrument [Line Items]                          
Stated interest rate (as a percent)                     3.60%    
Unamortized discount included in carrying value                   2,500,000 $ 2,200,000 2,500,000  
Interest rate on debt (as a percent)                     3.70%    
Senior Notes [Member] | 3.60% Senior Notes [Member] | Adjusted Treasury [Member]                          
Debt Instrument [Line Items]                          
Basis points used in determining redemption price prior to maturity                     300.00%    
Senior Notes [Member] | 5.250% Senior Notes [Member]                          
Debt Instrument [Line Items]                          
Stated interest rate (as a percent)                     5.25%    
Unamortized discount included in carrying value                   $ 4,200,000 $ 3,800,000 $ 4,200,000  
Interest rate on debt (as a percent)                     5.49%    
Senior Notes [Member] | 5.250% Senior Notes [Member] | Adjusted Treasury [Member]                          
Debt Instrument [Line Items]                          
Basis points used in determining redemption price prior to maturity                     400.00%    
Senior Notes [Member] | 4.25% Exchangeable Senior Notes [Member]                          
Debt Instrument [Line Items]                          
Stated interest rate (as a percent)                   4.25%   4.25%  
Operating properties, net [Member] | December 2013 Portfolio Conveyance [Member]                          
Debt Instrument [Line Items]                          
Gain (loss) on early extinguishment of debt           $ 67,800,000              
Debt settled through the surrender of real estate assets           $ 146,500,000              
Operating properties, net [Member] | 15000 and 15010 Conference Center Drive [Member] | Northern Virginia [Member]                          
Debt Instrument [Line Items]                          
Gain (loss) on early extinguishment of debt   84,800,000                      
Debt settled through the surrender of real estate assets   $ 150,000,000