Quarterly report pursuant to Section 13 or 15(d)

Investments In Unconsolidated Joint Ventures (Mack-Green-Gale LLC/Gramercy Agreement) (Details)

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Investments In Unconsolidated Joint Ventures (Mack-Green-Gale LLC/Gramercy Agreement) (Details) (USD $)
0 Months Ended 3 Months Ended 6 Months Ended 12 Months Ended 0 Months Ended 6 Months Ended 6 Months Ended 3 Months Ended 6 Months Ended 0 Months Ended
Dec. 17, 2010
Gramercy Agreement [Member]
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Apr. 29, 2009
Gramercy Agreement [Member]
Jun. 30, 2012
Gramercy Agreement [Member]
Jun. 30, 2011
Gramercy Agreement [Member]
Mar. 31, 2010
Gramercy Agreement [Member]
sqft
Mar. 31, 2009
Gramercy Agreement [Member]
Jun. 30, 2012
Gramercy Agreement [Member]
Jun. 30, 2011
Gramercy Agreement [Member]
Dec. 31, 2008
Gramercy Agreement [Member]
May 09, 2006
Mack-Green [Member]
Jun. 30, 2012
Mack-Green [Member]
Apr. 29, 2009
Mack-Green [Member]
Jun. 30, 2012
SL Green [Member]
Mar. 31, 2009
OPLP [Member]
Dec. 31, 2007
OPLP [Member]
May 09, 2006
OPLP [Member]
sqft
property
May 09, 2006
OPLP [Member]
Mack-Green [Member]
Jun. 30, 2012
Ten Operating Partnerships [Member]
Mack-Green [Member]
Jun. 30, 2012
Ten Operating Partnerships [Member]
SL Green [Member]
Jun. 30, 2012
Eight Operating Partnerships [Member]
Mack-Green [Member]
Jun. 30, 2012
Eight Operating Partnerships [Member]
SL Green [Member]
May 09, 2006
New Jersey [Member]
OPLP [Member]
sqft
property
May 09, 2006
Michigan [Member]
OPLP [Member]
property
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Schedule of Equity Method Investments [Line Items]                                              
Percentage of interest in venture                       100.00%       100.00% 96.00%            
Acquisition cost                   $ 125,000,000                          
Mortgage loans, carrying amount           90,300,000               276,300,000                  
Mortgage finance on property obtained 11,000,000                                            
Number of properties           6         4                        
Mortgage loan, maturity date             May 2009             May 2016                  
Area of office property sold, square feet 198,376       121,314                                   1,200,000
Area of office property, square feet                               3,500,000           2,300,000  
Spread over LIBOR   275       275                                  
Interest rate cap   3.15%                                          
Venture sale of real estate         13,900,000                   83,500,000                
Management, leasing and other services fees     112,000 113,000     237,000 274,000                              
Mortgage loans on real estate bearing weighted average fixed interest rate                           185,000,000                  
Weighted average fixed interest rate                           6.26%                  
Repayments of debt 26,800,000                                            
Number of owned office properties                               25           17  
Number of properties sold         1                                   8
Venture gain (loss) on sale of real estate                             (22,300,000)                
Profit sharing percentage                     50.00%   50.00%         99.00% 1.00% 1.00% 99.00%    
Impairment charge on property                 $ 32,300,000                            
Sharing percent of amount realized   50.00%                                          
Holding and distribution pattern under operating agreement                   The Mack-Green operating agreement generally provided for profits and losses to be allocated as follows:99 percent of Mack-Green's share of the profits and losses from 10 specific OPLP Properties allocable to the Company and one percent allocable to SL Green;(ii) one percent of Mack-Green's share of the profits and losses from eight specific OPLP Properties and its minor interest in four office properties allocable to the Company and 99 percent allocable to SL Green; and(iii) 50 percent of all other profits and losses allocable to the Company and 50 percent allocable to SL Green.