Corporate Indebtedness (Details 2) (USD $)			6 Months Ended		6 Months Ended					6 Months Ended				6 Months Ended				6 Months Ended				6 Months Ended				6 Months Ended				6 Months Ended				6 Months Ended				6 Months Ended
	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2014 3.00% Senior unsecured notes maturing on October 15, 2017	Oct. 31, 2010 3.00% Senior unsecured notes maturing on October 15, 2017	Jun. 30, 2013 4.0% exchangeable senior debentures due 2025	Jun. 30, 2014 4.0% exchangeable senior debentures due 2025	Mar. 31, 2007 3.0% exchangeable senior debentures due 2027	Jun. 30, 2014 Senior Unsecured Notes	Dec. 31, 2013 Senior Unsecured Notes	Jun. 30, 2014 Senior Unsecured Notes 5.88% Senior unsecured notes maturing on August 15, 2014		Dec. 31, 2013 Senior Unsecured Notes 5.88% Senior unsecured notes maturing on August 15, 2014		Jun. 30, 2014 Senior Unsecured Notes 6.00% Senior unsecured notes maturing on March 31, 2016		Dec. 31, 2013 Senior Unsecured Notes 6.00% Senior unsecured notes maturing on March 31, 2016		Jun. 30, 2014 Senior Unsecured Notes 3.00% Senior unsecured notes maturing on October 15, 2017		Dec. 31, 2013 Senior Unsecured Notes 3.00% Senior unsecured notes maturing on October 15, 2017		Jun. 30, 2014 Senior Unsecured Notes 5.00% senior unsecured notes maturing on August 15, 2018		Dec. 31, 2013 Senior Unsecured Notes 5.00% senior unsecured notes maturing on August 15, 2018		Jun. 30, 2014 Senior Unsecured Notes 7.75% Senior unsecured notes maturing on March 15, 2020		Dec. 31, 2013 Senior Unsecured Notes 7.75% Senior unsecured notes maturing on March 15, 2020		Jun. 30, 2014 Senior Unsecured Notes 4.50% senior unsecured notes maturing on December 1, 2022		Dec. 31, 2013 Senior Unsecured Notes 4.50% senior unsecured notes maturing on December 1, 2022		Jun. 30, 2014 Senior Unsecured Notes 4.0% exchangeable senior debentures due 2025		Dec. 31, 2013 Senior Unsecured Notes 4.0% exchangeable senior debentures due 2025		Jun. 30, 2014 Senior Unsecured Notes 3.0% exchangeable senior debentures due 2027		Dec. 31, 2013 Senior Unsecured Notes 3.0% exchangeable senior debentures due 2027
Mortgages and Other Loans Payable
Unpaid Principal Balance								$ 1,386,221,000		$ 75,898,000	[1]			$ 255,308,000	[1]			$ 345,000,000	[2]			$ 250,000,000	[3]			$ 250,000,000	[3]			$ 200,000,000	[3]			$ 7,000	[1],[4]			$ 10,008,000	[5]
Accreted Balance	2,127,206,000	1,739,330,000						1,344,206,000	1,339,330,000	75,898,000	[1]	75,898,000	[1]	255,227,000	[1]	255,206,000	[1]	303,354,000	[2]	297,837,000	[2]	249,712,000	[3]	249,681,000	[3]	250,000,000	[3]	250,000,000	[3]	200,000,000	[3]	200,000,000	[3]	7,000	[1],[4]	7,000	[1],[4]	10,008,000	[5]	10,701,000	[5]
Interest rate (as a percent)										5.88%	[1],[6]			6.00%	[1],[6]			3.00%	[2],[6]			5.00%	[3],[6]			7.75%	[3],[6]			4.50%	[3],[6]			4.00%	[1],[4],[6]			3.00%	[5],[6]
Effective Rate (as a percent)										5.88%	[1]			6.00%	[1]			3.00%	[2]			5.00%	[3]			7.75%	[3]			4.50%	[3]			4.00%	[1],[4]			3.00%	[5]
Term										10 years	[1]			10 years	[1]			7 years	[2]			7 years	[3]			10 years	[3]			10 years	[3]			20 years	[1],[4]			20 years	[5]
Premium on sale price to calculate exchange price of notes (as a percent)				30.00%			25.00%
Exchange price (in dollars per share)				$ 85.81		$ 1.3491	$ 173.30
Adjusted exchange rate for the debentures (in shares)			11.7153		7.7461
Amount of convertible debt recorded in equity				78,300,000
Debt Instrument, Unamortized Discount			$ 41,600,000

[1] Issued by ROP.

[2] Issued by the Operating Partnership. Interest on these exchangeable notes is payable semi-annually on April 15 and October 15. The notes had an initial exchange rate representing an exchange price that was set at a 30.0% premium to the last reported sale price of SL Green's common stock on October 6, 2010, or $85.81. The initial exchange rate is subject to adjustment under certain circumstances. The current exchange rate is 11.7153 shares of SL Green's common stock per $1,000 principal amount of these notes. The notes are senior unsecured obligations of the Operating Partnership and are exchangeable upon the occurrence of specified events and during the period beginning on the twenty-second scheduled trading day prior to the maturity date and ending on the second business day prior to the maturity date, into cash or a combination of cash and shares of SL Green's common stock, if any, at our option. The notes are guaranteed by ROP. On the issuance date, $78.3 million of the debt balance was recorded in equity. As of June 30, 2014, $41.6 million remained to be amortized into the debt balance.

[3] Issued by the Company, the Operating Partnership and ROP, as co-obligors.

[4] Exchangeable senior debentures which are currently callable at par. In addition, the debentures can be put to ROP, at the option of the holder at par plus accrued and unpaid interest, on June 15, 2015 and 2020 and upon the occurrence of certain change of control transactions. As a result of the acquisition of all outstanding shares of common stock of Reckson, or the Reckson Merger, the adjusted exchange rate for the debentures is 7.7461 shares of SL Green's common stock per $1,000 of principal amount of debentures and the adjusted reference dividend for the debentures is $1.3491.

[5] Issued by the Operating Partnership. Interest on these remaining exchangeable notes is payable semi-annually on March 30 and September 30. The notes have an initial exchange rate representing an exchange price that was set at a 25.0% premium to the last reported sale price of the Company's common stock on March 20, 2007, or $173.30. The initial exchange rate is subject to adjustment under certain circumstances. The notes are senior unsecured obligations of the Operating Partnership and are exchangeable upon the occurrence of specified events and during the period beginning on the twenty-second scheduled trading day prior to the maturity date and ending on the second business day prior to the maturity date, into cash or a combination of cash and shares of SL Green's common stock, if any, at our option. The notes are currently redeemable at the Operating Partnership’s option. The Operating Partnership may be required to repurchase the notes on March 30, 2017 and 2022, and upon the occurrence of certain designated events.

[6] Interest on the senior unsecured notes is payable semi-annually with principal and unpaid interest due on the scheduled maturity dates.