v2.4.0.6
Stock Option And Incentive Plan (Narrative) (Details) (USD $)
 3 Months Ended 12 Months Ended 0 Months Ended 3 Months Ended 0 Months Ended 3 Months Ended
Mar. 31, 2012
Mar. 31, 2012
TRS Component Sliding Scale One [Member]
Y
Mar. 31, 2012
TRS Component Sliding Scale Two [Member]
Mar. 31, 2012
TRS Component Sliding Scale Three [Member]
Y
Mar. 31, 2012
TRS Component Hypothetical Situation [Member]
Y
Dec. 31, 2011
OPP Units 2008 [Member]
Feb. 07, 2012
OPP Units 2012 [Member]
D
Jan. 25, 2012
OPP Units 2012 [Member]
Y
Mar. 31, 2012
OPP Units 2012 [Member]
D
Mar. 31, 2012
OPP Awards Vesting 2015 [Member]
OPP Units 2012 [Member]
Mar. 31, 2012
OPP Awards Vesting 2016 [Member]
OPP Units 2012 [Member]
Mar. 31, 2012
Opp Awards Vesting 2017 [Member]
OPP Units 2012 [Member]
Mar. 31, 2012
Minimum [Member]
TRS Component Sliding Scale Three [Member]
Mar. 31, 2012
Maximum [Member]
TRS Component Sliding Scale Three [Member]
Feb. 13, 2012
Executive Vice President [Member]
Y
M
Mar. 31, 2012
Executive Vice President [Member]
Feb. 13, 2012
2011 Outperformance Award [Member]
Executive Vice President [Member]
Stock Option And Incentive Plan And Stock Purchase Plan [Line Items]                                  
Award additional vesting period, years               2                  
Measurement Period For Outperformance Awards                 February 7, 2012 to February 6, 2015                
Start of the measurement period                 Feb. 07, 2012                
End of the measurement period                 Feb. 06, 2015                
Trading days prior to and including February 7, 2012             5                    
TRS measurement, years   3   3 3 3   3                  
Average closing price of common stock for five trading days prior and including February 7, 2012             $ 106.69                    
Aggregate rewards of OPP awards, maximum cap                 $ 40,000,000                
Excess total return above a cumulative absolute TRS hurdle                 2.00%                
Cumulative absolute TRS hurdle   24.00%     18.00%       24.00%       0.00% 24.00%      
Cumulative absolute TRS hurdle, annum     0.00%   6.00%       8.00%                
Measurement period for cumulative absolute TRS hurdle (years)                 3                
Excess or deficient total return of relative TRS hurdle equal to total return of REIT Index                 2.00%                
Percentage of the potential relative TRS component earned if the Company's TRS is equal to or greater than a cumulative 24% over three years   100.00%                              
Percentage earned if the Company's TRS is 0% or less     0.00%                            
Percentage calculated by linear interpolation earned if the Company's cumulative TRS over three years is between 0% and 24%, minimum       0.00%                          
Percentage calculated by linear interpolation earned if the Company's cumulative TRS over three years is between 0% and 24%, maximum       100.00%                          
Potential relative TRS component proration percentage         75.00%                        
Distributions percent before measurement date                 10.00%                
Vesting Percentage                   25.00% 25.00% 50.00%          
Vesting Date                   Feb. 07, 2015 Feb. 07, 2016 Feb. 07, 2017          
Performance measurement period, days                 15                
LTIP And Common Units Equivalency Ratio one-for-one                                
Cash payment related to resignation                             1,533,333    
Cash bonus for 2011 as part of resignation agreement                             950,000    
Consulting period, months                             2    
Consulting fee, per month                             20,000    
Accelerated share vesting with respect to LTIP units                             23,502    
Common shares received due to accelerated share vesting with respect to stock options                             4,464    
Accelerated share vesting with respect to common stock                             5,117    
Common stock exercise price per share for stock options                             $ 92.71    
Common stock exercise price per share for common stock                             $ 104.47    
Percentage of outperformance award retained                                 36.00%
Non-compete agreement, years                             1    
Expense recognized upon resignation                               $ 4,500,000