Consolidated Statements of Capital Statement (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Increase (Decrease) in Partner's Capital
Other comprehensive income	$ 8,406	$ 14,987	$ (1,530)
Issuance of units in the Operating Partnership	56,469	24,750	42,239
DRIP proceeds	64	67	99,570
Redemption of units	31,653	17,287	87,513
Redemption of preferred units		(192,500)	(200,013)
Preferred units issuance costs		(33)
Deferred compensation plan	(1,514)	166	(13,428)
Amortization of deferred compensation plan	29,749	26,329	28,742
Contributions-treasury shares		7,120
Cash distributions to noncontrolling interests	(7,019)	(14,623)	(21,946)
Common Stock
Increase (Decrease) in Partner's Capital
DRIP proceeds			13
DRIP proceeds (in shares)			1,305
Redemption of units	3	2	11
Redemption of units (in units)	315	239	1,096
Deferred compensation plan		2	3
Contributions-treasury shares (units)		83
Noncontrolling Interests
Increase (Decrease) in Partner's Capital
Cash distributions to noncontrolling interests	(7,019)	(14,623)	(21,946)
SL Green Operating Partnership
Increase (Decrease) in Partner's Capital
Beginning Balance	7,282,352	7,120,010	6,648,339
Net income	543,113	149,023	207,593
Other comprehensive income	8,406	14,987	(1,530)
Preferred distributions	(14,952)	(21,881)	(30,411)
Issuance of units in the Operating Partnership	56,469	24,750	42,239
DRIP proceeds	64	67	99,570
Redemption of units	0	0	0
Redemption of preferred units		(192,500)	(200,013)
Preferred units issuance costs		(33)
Deferred compensation plan	(1,514)	166	(13,428)
Amortization of deferred compensation plan	29,749	26,329	28,742
Contribution to consolidated joint venture interest	30,800	8,164	25,894
Contributions—net proceeds from preferred stock offering			221,965
Contributions—net proceeds from common stock offering	185,321	290,699	201,279
Contributions-treasury shares		7,120
Contributions - proceeds from stock options exercised	25,211	12,904	13,173
Cash distributions to noncontrolling interests	(7,019)	(14,623)	(21,946)
Cash distribution declared	(209,260)	(142,830)	(101,456)
Ending Balance	7,928,740	7,282,352	7,120,010
SL Green Operating Partnership \| General Partner
Increase (Decrease) in Partner's Capital
Beginning Balance	6,506,747	6,189,529	5,714,856
Balance (units)	94,993	91,250	85,783
Net income	503,104	113,490	165,994
DRIP proceeds	64	67	99,570
DRIP proceeds (in shares)		0	1,305
Redemption of units	31,653	17,287	87,513
Redemption of units (in units)	315	239	1,096
Redemption of preferred units		(12,160)	(10,010)
Deferred compensation plan (units)	15	135	43
Deferred compensation plan	(1,514)	166	(13,428)
Amortization of deferred compensation plan	29,749	26,329	28,742
Contributions—net proceeds from common stock offering	185,321	290,699	201,279
Contributions - net proceeds from common stock offering (in units)	1,654	3,062	2,640
Contributions-treasury shares		7,120
Contributions-treasury shares (units)		83
Contributions - proceeds from stock options exercised	25,211	12,904	13,173
Contributions - proceeds from stock options exercised (in units)	348	224	383
Cash distribution declared	(201,411)	(138,684)	(98,160)
Ending Balance	7,078,924	6,506,747	6,189,529
Balance (units)	97,325	94,993	91,250
SL Green Operating Partnership \| Limited Partners
Increase (Decrease) in Partner's Capital
Balance (units)	2,902	2,760	2,765
Issuance of units (in units)	1,386	381	801
Redemption of units (in units)	(315)	(239)	(1,096)
Deferred compensation plan (units)			290
Balance (units)	3,973	2,902	2,760
SL Green Operating Partnership \| Series C Preferred Stock
Increase (Decrease) in Partner's Capital
Beginning Balance		180,340	274,022
Net income		6,932	20,290
Preferred distributions		(6,932)	(20,290)
Redemption of preferred units		(180,340)	(93,682)
Ending Balance	0	0	180,340
SL Green Operating Partnership \| Series D Preferred Stock
Increase (Decrease) in Partner's Capital
Beginning Balance			96,321
Net income			4,266
Preferred distributions			(4,266)
Redemption of preferred units			(96,321)
Ending Balance	0	0	0
SL Green Operating Partnership \| Series I Preferred Stock
Increase (Decrease) in Partner's Capital
Beginning Balance	221,932	221,965	0
Net income	14,952	14,949	5,855
Preferred distributions	(14,952)	(14,949)	(5,855)
Preferred units issuance costs		(33)
Contributions—net proceeds from preferred stock offering			221,965
Ending Balance	221,932	221,932	221,965
SL Green Operating Partnership \| Common Stock \| Limited Partners
Increase (Decrease) in Partner's Capital
Beginning Balance	77,864	71,524	114,497
Net income	18,467	3,023	5,597
Issuance of units in the Operating Partnership	56,469	24,750	42,239
Redemption of units	(31,653)	(17,287)	(87,513)
Cash distribution declared	(7,849)	(4,146)	(3,296)
Ending Balance	113,298	77,864	71,524
SL Green Operating Partnership \| Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Partner's Capital
Beginning Balance	(15,662)	(30,649)	(29,119)
Other comprehensive income	8,406	14,987	(1,530)
Ending Balance	(7,256)	(15,662)	(30,649)
SL Green Operating Partnership \| Noncontrolling Interests
Increase (Decrease) in Partner's Capital
Beginning Balance	491,471	487,301	477,762
Net income	6,590	10,629	5,591
Contribution to consolidated joint venture interest	30,800	8,164	25,894
Cash distributions to noncontrolling interests	(7,019)	(14,623)	(21,946)
Ending Balance	$ 521,842	$ 491,471	$ 487,301

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