Consolidated Statements of Income (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	3 Months Ended				12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenues
Rental revenue, net					$ 1,080,684,000	$ 1,062,682,000	$ 947,479,000
Escalation and reimbursement					169,529,000	165,156,000	143,544,000
Investment income					193,843,000	119,155,000	120,418,000
Other income					25,021,000	35,736,000	35,418,000
Total revenues	346,599,000	357,011,000	344,535,000	334,585,000	1,469,077,000	1,382,729,000	1,246,859,000
Expenses
Operating expenses (including $18,728 (2013), $17,274 (2012) and $15,041 (2011) of related party expenses)					293,514,000	292,392,000	257,938,000
Real estate taxes					218,832,000	209,337,000	173,154,000
Ground rent					39,926,000	37,866,000	32,919,000
Interest expense, net of interest income					330,215,000	329,897,000	285,248,000
Amortization of deferred financing costs					16,695,000	19,450,000	14,108,000
Depreciation and amortization					337,692,000	325,737,000	271,306,000
Loan loss and other investment reserves, net of recoveries					0	564,000	6,722,000
Transaction related costs, net of recoveries					3,987,000	5,625,000	5,561,000
Marketing, general and administrative					86,192,000	82,840,000	80,103,000
Total expenses					1,327,053,000	1,303,708,000	1,127,059,000
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, (loss) gain on sale of investment in marketable securities, depreciable real estate reserves and (loss) gain on early extinguishment of debt					142,024,000	79,021,000	119,800,000
Equity in net income from unconsolidated joint ventures					9,921,000	76,418,000	1,583,000
Equity in net gain on sale of interest in unconsolidated joint venture/ real estate	19,277,000	(4,807,000)	15,323,000	7,260,000	3,601,000	37,053,000	2,918,000
Purchase price fair value adjustment					(2,305,000)	0	498,195,000
(Loss) gain on sale of investment in marketable securities					(65,000)	4,940,000	4,866,000
Depreciable real estate reserves					0	0	(5,789,000)
(Loss) gain on early extinguishment of debt	(6,978,000)	0	0	0	(18,518,000)	(6,978,000)	904,000
Income from continuing operations					134,658,000	190,454,000	622,477,000
Net income from discontinued operations	9,737,000	951,000	899,000	1,032,000	1,725,000	12,619,000	8,560,000
Gain on sale of discontinued operations	0	0	0	6,627,000	14,900,000	6,627,000	46,085,000
Net income					151,283,000	209,700,000	677,122,000
Net income attributable to noncontrolling interests:
Noncontrolling interests in the Operating Partnership					(3,023,000)	(5,597,000)	(14,629,000)
Noncontrolling interests in other partnerships					(10,629,000)	(5,591,000)	(15,083,000)
Preferred units distribution					(2,260,000)	(2,107,000)	0
Net income attributable to SL Green	27,363,000	25,657,000	110,584,000	32,801,000	135,371,000	196,405,000	647,410,000
Preferred stock redemption costs	0	(10,010,000)	0	0	(12,160,000)	(10,010,000)	0
Perpetual preferred stock dividends	(7,407,000)	(7,915,000)	(7,544,000)	(7,545,000)	(21,881,000)	(30,411,000)	(30,178,000)
Net income	19,956,000	7,732,000	103,040,000	25,256,000	101,330,000	155,984,000	617,232,000
Amounts attributable to SL Green common stockholders:
Income from continuing operations					83,927,000	101,638,000	74,341,000
Purchase price fair value adjustment					(2,239,000)	0	486,660,000
Equity in net gain on sale of interest in unconsolidated joint venture/real estate					3,496,000	35,769,000	2,850,000
Net income from discontinued operations					1,675,000	12,180,000	8,363,000
Gain on sale of discontinued operations					14,471,000	6,397,000	45,018,000
Net income	19,956,000	7,732,000	103,040,000	25,256,000	101,330,000	155,984,000	617,232,000
Basic earnings per share:
Income from continuing operations before discontinued operations (usd per share)					$ 0.89	$ 1.14	$ 6.70
Equity in net gain on sale of interest in unconsolidated joint venture/real estate (usd per share)					$ 0.04	$ 0.40	$ 0.03
Net income from discontinued operations (usd per share)					$ 0.02	$ 0.14	$ 0.10
Gain on sale of discontinued operations (usd per share)					$ 0.15	$ 0.07	$ 0.54
Net income attributable to SL Green common stockholders (usd per share)	$ 0.22	$ 0.09	$ 1.15	$ 0.29	$ 1.10	$ 1.75	$ 7.37
Diluted earnings per share:
Income from continuing operations before discontinued operations (usd per share)					$ 0.88	$ 1.13	$ 6.67
Equity in net gain on sale of interest in unconsolidated joint venture/real estate (usd per share)					$ 0.04	$ 0.40	$ 0.03
Net income from discontinued operations (usd per share)					$ 0.02	$ 0.14	$ 0.10
Gain on sale of discontinued operations (usd per share)					$ 0.16	$ 0.07	$ 0.53
Net income attributable to SL Green common stockholders (usd per share)	$ 0.22	$ 0.09	$ 1.14	$ 0.29	$ 1.10	$ 1.74	$ 7.33
Basic weighted average common shares outstanding (in shares)					92,269	89,319	83,762
Diluted weighted average common shares and common share equivalents outstanding (usd per share)					95,266	92,873	86,244
Noncontrolling Interest [Abstract]
Purchase price fair value adjustment					(2,305,000)	0	498,195,000
SL Green Operating Partnership
Revenues
Rental revenue, net					1,080,684,000	1,062,682,000	947,479,000
Escalation and reimbursement					169,529,000	165,156,000	143,544,000
Investment income					193,843,000	119,155,000	120,418,000
Other income					25,021,000	35,736,000	35,418,000
Total revenues	346,598,000	357,011,000	344,535,000	334,585,000	1,469,077,000	1,382,729,000	1,246,859,000
Expenses
Operating expenses (including $18,728 (2013), $17,274 (2012) and $15,041 (2011) of related party expenses)					293,514,000	292,392,000	257,938,000
Real estate taxes					218,832,000	209,337,000	173,154,000
Ground rent					39,926,000	37,866,000	32,919,000
Interest expense, net of interest income					330,215,000	329,897,000	285,248,000
Amortization of deferred financing costs					16,695,000	19,450,000	14,108,000
Depreciation and amortization					337,692,000	325,737,000	271,306,000
Loan loss and other investment reserves, net of recoveries					0	564,000	6,722,000
Transaction related costs, net of recoveries					3,987,000	5,625,000	5,561,000
Marketing, general and administrative					86,192,000	82,840,000	80,103,000
Total expenses					1,327,053,000	1,303,708,000	1,127,059,000
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, (loss) gain on sale of investment in marketable securities, depreciable real estate reserves and (loss) gain on early extinguishment of debt					142,024,000	79,021,000	119,800,000
Equity in net income from unconsolidated joint ventures					9,921,000	76,418,000	1,583,000
Equity in net gain on sale of interest in unconsolidated joint venture/ real estate	19,277,000	(4,807,000)	15,323,000	7,260,000	3,601,000	37,053,000	2,918,000
Purchase price fair value adjustment					(2,305,000)	0	498,195,000
(Loss) gain on sale of investment in marketable securities					(65,000)	4,940,000	4,866,000
Depreciable real estate reserves					0	0	(5,789,000)
(Loss) gain on early extinguishment of debt	(6,978,000)	0	0	0	(18,518,000)	(6,978,000)	904,000
Income from continuing operations					134,658,000	190,454,000	622,477,000
Net income from discontinued operations	9,737,000	951,000	899,000	1,032,000	1,725,000	12,619,000	8,560,000
Gain on sale of discontinued operations	0	0	0	6,627,000	14,900,000	6,627,000	46,085,000
Net income					151,283,000	209,700,000	677,122,000
Net income attributable to noncontrolling interests:
Noncontrolling interests in other partnerships					(10,629,000)	(5,591,000)	(15,083,000)
Net income attributable to SL Green					138,394,000	202,002,000	662,039,000
Preferred stock redemption costs	0	(10,010,000)	0	0
Perpetual preferred stock dividends	(7,407,000)	(7,915,000)	(7,544,000)	(7,545,000)
Net income					104,353,000	161,581,000	631,861,000
Amounts attributable to SL Green common stockholders:
Income from continuing operations					86,432,000	105,282,000	76,103,000
Equity in net gain on sale of interest in unconsolidated joint venture/real estate					3,601,000	37,053,000	2,918,000
Gain on sale of discontinued operations					14,900,000	6,627,000	46,085,000
Net income					104,353,000	161,581,000	631,861,000
Basic earnings per share:
Equity in net gain on sale of interest in unconsolidated joint venture/real estate (usd per share)					$ 0.04	$ 0.40	$ 0.03
Gain on sale of discontinued operations (usd per share)					$ 0.15	$ 0.07	$ 0.54
Net income attributable to SL Green common stockholders (usd per share)	$ 0.22	$ 0.09	$ 1.15	$ 0.29
Diluted earnings per share:
Equity in net gain on sale of interest in unconsolidated joint venture/real estate (usd per share)					$ 0.04	$ 0.40	$ 0.03
Gain on sale of discontinued operations (usd per share)					$ 0.16	$ 0.07	$ 0.53
Net income attributable to SL Green common stockholders (usd per share)	$ 0.22	$ 0.09	$ 1.14	$ 0.29
Noncontrolling Interest [Abstract]
Preferred unit distributions					(2,260,000)	(2,107,000)	0
Preferred unit redemption costs					(12,160,000)	(10,010,000)	0
Perpetual preferred unit distributions					(21,881,000)	(30,411,000)	(30,178,000)
Net income attributable to SLGOP common unitholders	20,677,000	8,299,000	106,461,000	26,144,000	104,353,000	161,581,000	631,861,000
Purchase price fair value adjustment					(2,305,000)	0	498,195,000
Net income from discontinued operations					$ 1,725,000	$ 12,619,000	$ 8,560,000
Net income from continuing operations before gains on sale and discontinued operations (in dollars per share)					$ 0.89	$ 1.14	$ 6.70
Net income from discontinued operations (in dollars per share)					$ 0.02	$ 0.14	$ 0.10
Net income attributable to SL Green common stockholders (in dollars per share)					$ 1.10	$ 1.75	$ 7.37
Net income from continuing operations before gains on sale and discontinued operations (in dollars per share)					$ 0.88	$ 1.13	$ 6.67
Net income from discontinued operations (in dollars per share)					$ 0.02	$ 0.14	$ 0.10
Net income attributable to SL Green common stockholders (in dollars per share)					$ 1.10	$ 1.74	$ 7.33
Basic weighted average common shares outstanding (in shares)					95,004	92,526	85,747
Diluted weighted average common shares and common share equivalents outstanding (in shares)					95,266	92,873	86,244