Segment Information (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Reconciliation of income from continuing operations to net income attributable to SL Green common stockholders
Income from continuing operations before equity in net gain on sale of unconsolidated joint venture / partial interest and purchase price fair value adjustments	$ 33,214	$ 11,341	$ 163,484	$ 115,896
Purchase price fair value adjustment		999		489,889
Equity in net gain (loss) on sale of interest in unconsolidated joint venture/real estate	(4,807)	3,032	11,987	3,032
Income from continuing operations	28,407	15,372	175,471	608,817
Net income from discontinued operations	223	1,116	145	4,665
Gain on sale of discontinued operations			6,627	46,085
Net income	28,630	16,488	182,243	659,567
Noncontrolling interests in the operating partnership	(567)	(170)	(4,876)	(13,946)
Noncontrolling interests in other partnerships	(1,835)	(1,694)	(6,792)	(8,564)
Preferred units distributions	(571)		(1,533)
Net income attributable to SL Green	25,657	14,624	169,042	637,057
Preferred stock redemption costs	(10,010)		(10,010)
Preferred stock dividends	(7,915)	(7,545)	(23,004)	(22,634)
Net income attributable to SL Green common stockholders	$ 7,732	$ 7,079	$ 136,028	$ 614,423