Segment Information (Schedule of Reconciliation of Income from Continuing Operations to Net Income Attributable to SL Green Common Stockholders)(Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
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 interest in unconsolidated joint venture/real estate and gain on sale of real estate	$ 8,815	$ 42,226
Equity in net gain on sale of interest in unconsolidated joint venture/real estate	9,915	0
Gain on sale of real estate, net	13,773	0
Income from continuing operations	32,503	42,226
Net income from discontinued operations	0	427
Gain on sale of discontinued operations	0	12,983
Net income	$ 32,503	$ 55,636