Partners' Capital of the Operating Partnership (EPS) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Stockholders' Equity
Net income (loss) attributable to SLGOP common unitholders	$ 133,457	$ (39,106)	$ 156,678	$ 4,171
Weighted average common shares outstanding (shares)	100,134,000	99,579,000	100,093,000	98,994,000
Common stock shares excluded from the diluted shares outstanding (shares)	739,636	845,026	228,122	748,000
Common stock shares excluded from the diluted shares outstanding due to net loss (shares)		4,367,272
SL Green Operating Partnership
Stockholders' Equity
Net income (loss) attributable to SLGOP common unitholders	$ 139,043	$ (40,683)	$ 163,186	$ 4,337
Weighted average common shares outstanding (shares)	104,476,000	103,487,000	104,251,000	102,930,000
Stock-based compensation plans (shares)	316,000	0	282,000	493,000
Diluted weighted average common units outstanding (shares)	104,792,000	103,487,000	104,533,000	103,423,000
Common stock shares excluded from the diluted shares outstanding (shares)	739,636	228,122	845,026	748,000
Common stock shares excluded from the diluted shares outstanding due to net loss (shares)		459,216