Consolidated Statements of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues
Rental revenue, net	$ 1,121,066	$ 996,782	$ 984,079
Escalation and reimbursement	164,376	155,965	151,187
Investment income	178,815	193,843	119,155
Other income	55,721	24,475	35,631
Total revenues	1,519,978	1,371,065	1,290,052
Expenses
Operating expenses, including $19,308 (2014), $19,152 (2013) and $17,645 (2012) of related party expenses	282,283	276,589	275,872
Real estate taxes	217,843	203,076	194,371
Ground rent	32,307	31,951	31,504
Interest expense, net of interest income	317,400	310,894	309,681
Amortization of deferred financing costs	22,377	15,855	18,558
Depreciation and amortization	371,610	324,461	311,860
Loan loss and other investment reserves, net of recoveries	0	0	564
Transaction related costs, net of recoveries	8,707	3,985	5,402
Marketing, general and administrative	92,488	86,192	82,840
Total expenses	1,345,015	1,253,003	1,230,652
Income from continuing operations before equity in net income from unconsolidated joint ventures, equity in net gain on sale of interest in unconsolidated joint venture/real estate, purchase price fair value adjustment, gain (loss) on sale of investment in marketable securities and loss on early extinguishment of debt	174,963	118,062	59,400
Equity in net income from unconsolidated joint ventures	26,537	9,921	76,418
Equity in net gain on sale of interest in unconsolidated joint venture/real estate	123,253	3,601	37,053
Purchase price fair value adjustment	67,446	(2,305)	0
Gain (loss) on sale of investment in marketable securities	3,895	(65)	4,940
Loss on early extinguishment of debt	(32,365)	(18,518)	(6,978)
Income from continuing operations	363,729	110,696	170,833
Net income from discontinued operations	19,075	25,687	32,240
Gain on sale of discontinued operations	163,059	14,900	6,627
Net income	545,863	151,283	209,700
Net income attributable to noncontrolling interests:
Noncontrolling interests in the Operating Partnership	(18,467)	(3,023)	(5,597)
Noncontrolling interests in other partnerships	(6,590)	(10,629)	(5,591)
Preferred units distributions	(2,750)	(2,260)	(2,107)
Net income attributable to SL Green	518,056	135,371	196,405
Preferred stock redemption costs	0	(12,160)	(10,010)
Perpetual preferred stock dividends	(14,952)	(21,881)	(30,411)
Amounts attributable to SL Green common stockholders:
Income from continuing operations before gains on sale and discontinued operations	143,466	60,654	82,696
Purchase price fair value adjustment	65,059	(2,239)	0
Equity in net gain on sale of interest in unconsolidated joint venture/real estate	118,891	3,497	35,769
Net income from discontinued operations	18,400	24,947	31,122
Gain on sale of discontinued operations	157,288	14,471	6,397
Net income attributable to SL Green common stockholders	503,104	101,330	155,984
Basic earnings per share:
Income from continuing operations before discontinued operations (usd per share)	$ 2.18	$ 0.64	$ 0.93
Equity in net gain on sale of interest in unconsolidated joint venture/real estate (usd per share)	$ 1.24	$ 0.04	$ 0.40
Net income from discontinued operations (usd per share)	$ 0.19	$ 0.27	$ 0.35
Gain on sale of discontinued operations (usd per share)	$ 1.64	$ 0.15	$ 0.07
Net income attributable to SL Green common stockholders (usd per share)	$ 5.25	$ 1.10	$ 1.75
Diluted earnings per share:
Income from continuing operations before discontinued operations (usd per share)	$ 2.17	$ 0.63	$ 0.92
Equity in net gain on sale of interest in unconsolidated joint venture/real estate (usd per share)	$ 1.24	$ 0.04	$ 0.40
Net income from discontinued operations (usd per share)	$ 0.19	$ 0.27	$ 0.35
Gain on sale of discontinued operations (usd per share)	$ 1.63	$ 0.16	$ 0.07
Net income attributable to SL Green common stockholders (usd per share)	$ 5.23	$ 1.10	$ 1.74
Basic weighted average common shares outstanding (in shares)	95,774	92,269	89,319
Diluted weighted average common shares and common share equivalents outstanding (in shares)	99,696	95,266	92,873
SL Green Operating Partnership
Revenues
Rental revenue, net	1,121,066	996,782	984,079
Escalation and reimbursement	164,376	155,965	151,187
Investment income	178,815	193,843	119,155
Other income	55,721	24,475	35,631
Total revenues	1,519,978	1,371,065	1,290,052
Expenses
Operating expenses, including $19,308 (2014), $19,152 (2013) and $17,645 (2012) of related party expenses	282,283	276,589	275,872
Real estate taxes	217,843	203,076	194,371
Ground rent	32,307	31,951	31,504
Interest expense, net of interest income	317,400	310,894	309,681
Amortization of deferred financing costs	22,377	15,855	18,558
Depreciation and amortization	371,610	324,461	311,860
Loan loss and other investment reserves, net of recoveries	0	0	564
Transaction related costs, net of recoveries	8,707	3,985	5,402
Marketing, general and administrative	92,488	86,192	82,840
Total expenses	1,345,015	1,253,003	1,230,652
Income from continuing operations before equity in net income from unconsolidated joint ventures, equity in net gain on sale of interest in unconsolidated joint venture/real estate, purchase price fair value adjustment, gain (loss) on sale of investment in marketable securities and loss on early extinguishment of debt	174,963	118,062	59,400
Equity in net income from unconsolidated joint ventures	26,537	9,921	76,418
Equity in net gain on sale of interest in unconsolidated joint venture/real estate	123,253	3,601	37,053
Purchase price fair value adjustment	67,446	(2,305)	0
Gain (loss) on sale of investment in marketable securities	3,895	(65)	4,940
Loss on early extinguishment of debt	(32,365)	(18,518)	(6,978)
Income from continuing operations	363,729	110,696	170,833
Net income from discontinued operations	19,075	25,687	32,240
Gain on sale of discontinued operations	163,059	14,900	6,627
Net income	545,863	151,283	209,700
Net income attributable to noncontrolling interests:
Noncontrolling interests in other partnerships	(6,590)	(10,629)	(5,591)
Net income attributable to SL Green	536,523	138,394	202,002
Amounts attributable to SL Green common stockholders:
Income from continuing operations before gains on sale and discontinued operations	148,738	62,470	85,661
Equity in net gain on sale of interest in unconsolidated joint venture/real estate	123,253	3,601	37,053
Gain on sale of discontinued operations	163,059	14,900	6,627
Basic earnings per share:
Equity in net gain on sale of interest in unconsolidated joint venture/real estate (usd per share)	$ 1.24	$ 0.04	$ 0.40
Gain on sale of discontinued operations (usd per share)	$ 1.64	$ 0.15	$ 0.07
Diluted earnings per share:
Equity in net gain on sale of interest in unconsolidated joint venture/real estate (usd per share)	$ 1.24	$ 0.04	$ 0.40
Gain on sale of discontinued operations (usd per share)	$ 1.63	$ 0.16	$ 0.07
Noncontrolling Interest [Abstract]
Preferred unit distributions	(2,750)	(2,260)	(2,107)
Preferred unit redemption costs	0	(12,160)	(10,010)
Perpetual preferred unit distributions	(14,952)	(21,881)	(30,411)
Net income attributable to SLGOP common unitholders	521,571	104,353	161,581
Purchase price fair value adjustment	67,446	(2,305)	0
Net income from discontinued operations	$ 19,075	$ 25,687	$ 32,240
Net income from continuing operations before gains on sale and discontinued operations (in dollars per share)	$ 2.18	$ 0.64	$ 0.93
Net income from discontinued operations (in dollars per share)	$ 0.19	$ 0.27	$ 0.35
Net income attributable to SL Green common stockholders (in dollars per share)	$ 5.25	$ 1.10	$ 1.75
Net income from continuing operations before gains on sale and discontinued operations (in dollars per share)	$ 2.17	$ 0.63	$ 0.92
Net income from discontinued operations (in dollars per share)	$ 0.19	$ 0.27	$ 0.35
Net income attributable to SL Green common stockholders (in dollars per share)	$ 5.23	$ 1.10	$ 1.74
Basic weighted average common shares outstanding (in shares)	99,288	95,004	92,526
Diluted weighted average common shares and common share equivalents outstanding (in shares)	99,696	95,266	92,873