Corporate Indebtedness (Details) (USD $)	3 Months Ended								12 Months Ended					1 Months Ended		1 Months Ended	12 Months Ended						12 Months Ended			12 Months Ended			0 Months Ended			1 Months Ended	12 Months Ended			1 Months Ended	12 Months Ended	1 Months Ended			12 Months Ended													12 Months Ended				12 Months Ended				12 Months Ended				12 Months Ended				12 Months Ended				12 Months Ended				12 Months Ended				12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Nov. 30, 2012	Dec. 31, 2013 Joint venture	Nov. 30, 2012 2012 Credit Facility	Dec. 31, 2013 2012 Credit Facility	Nov. 30, 2012 Revolving credit facility extenstion_option	Dec. 31, 2013 Revolving credit facility	Dec. 31, 2013 Revolving credit facility Maximum	Dec. 31, 2013 Revolving credit facility Minimum	Dec. 31, 2013 Term loan	Nov. 30, 2012 Term loan	Dec. 31, 2013 2011 Revolving Credit Facility	Dec. 31, 2013 2011 Revolving Credit Facility Maximum	Dec. 31, 2013 2011 Revolving Credit Facility Minimum	Dec. 31, 2013 2007 Revolving Credit Facility	Dec. 31, 2013 2007 Revolving Credit Facility Maximum	Dec. 31, 2013 2007 Revolving Credit Facility Minimum	Dec. 31, 2013 Senior Unsecured Notes	Dec. 27, 2012 6.00% Senior unsecured notes maturing on March 31, 2016	Dec. 27, 2012 5.875% Senior Unsecured Notes	Dec. 27, 2012 6.00% Senior Unsecured Notes	Oct. 31, 2010 3.00% Senior unsecured notes maturing on October 15, 2017	Dec. 31, 2013 3.00% Senior unsecured notes maturing on October 15, 2017	Dec. 31, 2012 4.0% exchangeable senior debentures due 2025	Dec. 31, 2013 4.0% exchangeable senior debentures due 2025	Mar. 31, 2007 3.0% exchangeable senior debentures due 2027	Dec. 31, 2013 3.0% exchangeable senior debentures due 2027	Jun. 30, 2005 Term Loans and Trust Preferred Securities	Dec. 31, 2013 Term Loans and Trust Preferred Securities	Dec. 31, 2013 Mortgages and other loans payable	Dec. 31, 2013 LIBOR Revolving credit facility	Dec. 31, 2013 LIBOR Revolving credit facility Maximum	Dec. 31, 2013 LIBOR Revolving credit facility Minimum	Dec. 31, 2013 LIBOR Term loan	Dec. 31, 2013 LIBOR Term loan Maximum	Dec. 31, 2013 LIBOR Term loan Minimum	Dec. 31, 2013 LIBOR 2011 Revolving Credit Facility Maximum	Dec. 31, 2013 LIBOR 2011 Revolving Credit Facility Minimum	Dec. 31, 2013 LIBOR 2007 Revolving Credit Facility Maximum	Dec. 31, 2013 LIBOR 2007 Revolving Credit Facility Minimum	Dec. 31, 2013 LIBOR Term Loans and Trust Preferred Securities	Dec. 31, 2013 Senior Unsecured Notes	Dec. 31, 2012 Senior Unsecured Notes	Dec. 31, 2013 Senior Unsecured Notes 5.88% Senior unsecured notes maturing on August 15, 2014		Dec. 31, 2012 Senior Unsecured Notes 5.88% Senior unsecured notes maturing on August 15, 2014		Dec. 31, 2013 Senior Unsecured Notes 6.00% Senior unsecured notes maturing on March 31, 2016		Dec. 31, 2012 Senior Unsecured Notes 6.00% Senior unsecured notes maturing on March 31, 2016		Dec. 31, 2013 Senior Unsecured Notes 3.00% Senior unsecured notes maturing on October 15, 2017		Dec. 31, 2012 Senior Unsecured Notes 3.00% Senior unsecured notes maturing on October 15, 2017		Dec. 31, 2013 Senior Unsecured Notes 5.00% senior unsecured notes maturing on August 15, 2018		Dec. 31, 2012 Senior Unsecured Notes 5.00% senior unsecured notes maturing on August 15, 2018		Dec. 31, 2013 Senior Unsecured Notes 7.75% Senior unsecured notes maturing on March 15, 2020		Dec. 31, 2012 Senior Unsecured Notes 7.75% Senior unsecured notes maturing on March 15, 2020		Dec. 31, 2013 Senior Unsecured Notes 4.50% senior unsecured notes maturing on December 1, 2022		Dec. 31, 2012 Senior Unsecured Notes 4.50% senior unsecured notes maturing on December 1, 2022		Dec. 31, 2013 Senior Unsecured Notes 4.0% exchangeable senior debentures due 2025		Dec. 31, 2012 Senior Unsecured Notes 4.0% exchangeable senior debentures due 2025		Dec. 31, 2013 Senior Unsecured Notes 3.0% exchangeable senior debentures due 2027		Dec. 31, 2012 Senior Unsecured Notes 3.0% exchangeable senior debentures due 2027
Corporate Indebtedness
Line of Credit Facility, Extension Fee, Percentage																	0.10%
Revolving credit facility, maximum borrowing capacity	$ 300,000,000.0								$ 300,000,000.0			$ 1,600,000,000.0				$ 1,200,000,000.0					$ 400,000,000.0	$ 1,500,000,000			$ 1,500,000,000
Number of extension options (extension options)																2
Extension option available														6 months
Maximum borrowing capacity, optional expansion																1,500,000,000.0
Interest rate added to base rate (as a percent)																																									1.45%	1.75%	1.00%	1.65%	2.00%	1.15%	1.85%	1.00%	1.10%	0.70%	1.25%
Fee on the unused balance, payable quarterly in arrears (as a percent)																		0.35%	0.15%				0.45%	0.175%		0.20%	0.125%
Facility fee on total commitments, payable quarterly in arrears (as a percent)																			0.30%
Letters of credit															74,600,000
Outstanding under line of credit facility	220,000,000				70,000,000				220,000,000	70,000,000							220,000,000			400,000,000
Ability to borrow under line of credit facility															900,000,000
Debt disclosures by scheduled maturity date
Unpaid Principal Balance																																																				1,386,914,000		75,898,000	[1],[2]			255,308,000	[1],[2]			345,000,000	[3]			250,000,000	[4]			250,000,000	[4]			200,000,000	[4]			7,000	[2],[5]			10,701,000	[6]
Accreted Balance	1,739,330,000				1,734,956,000				1,739,330,000	1,734,956,000																																										1,339,330,000	1,334,956,000	75,898,000	[1],[2]	75,898,000	[1],[2]	255,206,000	[1],[2]	255,165,000	[1],[2]	297,837,000	[3]	287,373,000	[3]	249,681,000	[4]	249,620,000	[4]	250,000,000	[4]	250,000,000	[4]	200,000,000	[4]	200,000,000	[4]	7,000	[2],[5]	7,000	[2],[5]	10,701,000	[6]	16,893,000	[6]
Coupon Rate (as a percent)																														5.875%	6.00%		3.00%		4.00%		3.00%		5.61%															5.88%	[1],[2],[7]			6.00%	[1],[2],[7]			3.00%	[3],[7]			5.00%	[4],[7]			7.75%	[4],[7]			4.50%	[4],[7]			4.00%	[2],[5],[7]			3.00%	[6],[7]
Effective Rate (as a percent)																	1.62%			2.00%																																		5.88%	[1],[2]			6.00%	[1],[2]			3.00%	[3]			5.00%	[4]			7.75%	[4]			4.50%	[4]			4.00%	[2],[5]			3.00%	[6]
Term																																																						10 years	[1],[2]			10 years	[1],[2]			7 years	[3]			7 years	[4]			10 years	[4]			10 years	[4]			20 years	[2],[5]			20 years	[6]
Aggregate principal amount of notes repurchased																													42,400,000	22,700,000	19,700,000			650,000			6,200,000
Repayment of debt																													46,400,000							102,200,000
Loss (gain) on early extinguishment of debt	(5,000)	0	10,000	18,513,000	6,978,000	0	0	0	18,518,000	6,978,000	(904,000)																		(3,800,000)
Debt instrument issued, value																																345,000,000				750,000,000		100,000,000
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				66,600,000
Debt Instrument, Unamortized Discount																																	47,200,000
Number of years for which securities will bear fixed rate of interest																																						10 years
Scheduled Amortization
2014																																								43,976,000
2015																																								47,312,000
2016																																								55,938,000
2017																																								61,213,000
2018																																								64,205,000
Thereafter																																								247,407,000
Total amortization of debt																																								520,051,000
Principal Repayments
2014													398,312,000																											237,273,000
2015													45,332,000																											229,537,000
2016													604,510,000																											594,017,000
2017													930,338,000																											1,086,579,000
2018													28,000																											21,363,000
Thereafter													173,944,000																											2,171,758,000
Total principal repayments													2,152,464,000																											4,340,527,000
Scheduled Amortization and Principal Repayments
2014	357,147,000								357,147,000																			75,898,000
2015	276,856,000								276,856,000																			7,000
2016	905,263,000								905,263,000																			255,308,000
2017	1,723,493,000								1,723,493,000													220,000,000						355,701,000
2018	735,568,000								735,568,000																			650,000,000
Thereafter	2,969,165,000								2,969,165,000													0						450,000,000											100,000,000
Total amortization of debt and principal repayments	6,967,492,000								6,967,492,000													220,000,000						1,786,914,000											100,000,000
Interest expense
Interest expense									332,276,000	331,516,000	287,252,000
Interest income									(2,061,000)	(1,619,000)	(2,004,000)
Interest expense, net									330,215,000	329,897,000	285,248,000
Interest capitalized									$ 11,475,000	$ 12,218,000	$ 5,123,000

[1] On December 27, 2012, we repurchased $42.4 million of aggregate principal amount of these notes, consisting of $22.7 million of the 5.875% Notes and $19.7 million of the 6.0% Notes, for a total consideration of $46.4 million and realized a net loss on early extinguishment of debt of approximately $3.8 million.

[2] Issued by ROP.

[3] In October 2010, the Operating Partnership issued $345.0 million of these exchangeable notes. Interest on these 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 December 31, 2013, approximately $47.2 million remained to be amortized into the debt balance.

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

[5] 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. During the year ended December 31, 2012, we repurchased $650,000 of these bonds at par.

[6] In March 2007, the Operating Partnership issued $750.0 million of these exchangeable notes. Interest on these 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. On March 30, 2012, we repurchased $102.2 million of aggregate principal amount of the exchangeable notes pursuant to a mandatory offer to repurchase the notes. On the issuance date, $66.6 million was recorded in equity and was fully amortized into the debt balance as of March 31, 2012. During the year ended December 31, 2013, we repurchased $6.2 million of aggregate principal amount of exchangeable notes at approximately at par.

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