Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues
Rental revenue, net	$ 804,423	$ 983,557	$ 978,574
Investment income	120,163	195,590	201,492
Other income	128,158	59,848	47,326
Total revenues	1,052,744	1,238,995	1,227,392
Expenses
Operating expenses, including $12,643 in 2020, $18,106 in 2019, $17,823 in 2018 of related party expenses	183,200	234,676	229,347
Real estate taxes	176,315	190,764	186,351
Operating lease rent	29,043	33,188	32,965
Interest expense, net of interest income	116,679	190,521	208,669
Amortization of deferred financing costs	11,794	11,653	12,408
Depreciation and amortization	313,668	272,358	279,507
Loan loss and other investment reserves, net of recoveries	35,298	0	6,839
Transaction related costs	503	729	1,099
Marketing, general and administrative	91,826	100,875	92,631
Total expenses	958,326	1,034,764	1,049,816
Equity in net (loss) income from unconsolidated joint ventures	(25,195)	(34,518)	7,311
Equity in net gain on sale of interest in unconsolidated joint venture/real estate	2,961	76,181	303,967
Purchase price and other fair value adjustment	187,522	69,389	57,385
Gain (loss) on sale of real estate, net	215,506	(16,749)	(30,757)
Depreciable real estate reserves and impairments	(60,454)	(7,047)	(227,543)
Loss on early extinguishment of debt	0	0	(17,083)
Net income	414,758	291,487	270,856
Net income attributable to noncontrolling interests:
Noncontrolling interests in the Operating Partnership	(20,016)	(13,301)	(12,216)
Net loss attributable to noncontrolling interests in other partnerships	(14,940)	3,159	6
Preferred unit distributions	(8,747)	(10,911)	(11,384)
Net income (loss) attributable to SL Green/SLGOP	371,055	270,434	247,262
Perpetual preferred stock dividends	(14,950)	(14,950)	(14,950)
Net income attributable to SL Green common stockholders	$ 356,105	$ 255,484	$ 232,312
Basic earnings per share (in dollars per share)	$ 4.88	$ 3.20	$ 2.75
Diluted earnings per share (in dollars per share)	$ 4.87	$ 3.19	$ 2.75
Basic weighted average common shares outstanding (in shares)	72,552	79,415	84,090
Diluted weighted average common shares and common share equivalents outstanding (in shares)	77,243	84,234	89,071
SL Green Operating Partnership
Revenues
Rental revenue, net	$ 804,423	$ 983,557	$ 978,574
Investment income	120,163	195,590	201,492
Other income	128,158	59,848	47,326
Total revenues	1,052,744	1,238,995	1,227,392
Expenses
Operating expenses, including $12,643 in 2020, $18,106 in 2019, $17,823 in 2018 of related party expenses	183,200	234,676	229,347
Real estate taxes	176,315	190,764	186,351
Operating lease rent	29,043	33,188	32,965
Interest expense, net of interest income	116,679	190,521	208,669
Amortization of deferred financing costs	11,794	11,653	12,408
Depreciation and amortization	313,668	272,358	279,507
Loan loss and other investment reserves, net of recoveries	35,298	0	6,839
Transaction related costs	503	729	1,099
Marketing, general and administrative	91,826	100,875	92,631
Total expenses	958,326	1,034,764	1,049,816
Equity in net (loss) income from unconsolidated joint ventures	(25,195)	(34,518)	7,311
Equity in net gain on sale of interest in unconsolidated joint venture/real estate	2,961	76,181	303,967
Purchase price and other fair value adjustment	187,522	69,389	57,385
Gain (loss) on sale of real estate, net	215,506	(16,749)	(30,757)
Depreciable real estate reserves and impairments	(60,454)	(7,047)	(227,543)
Loss on early extinguishment of debt	0	0	(17,083)
Net income	414,758	291,487	270,856
Net income attributable to noncontrolling interests:
Net loss attributable to noncontrolling interests in other partnerships	(14,940)	3,159	6
Preferred unit distributions	(8,747)	(10,911)	(11,384)
Net income (loss) attributable to SL Green/SLGOP	391,071	283,735	259,478
Perpetual preferred stock dividends	(14,950)	(14,950)	(14,950)
Net income attributable to SLGOP common unitholders	$ 376,121	$ 268,785	$ 244,528
Basic earnings per unit (in dollars per share)	$ 4.88	$ 3.19	$ 2.75
Diluted earnings per unit (in dollars per share)	$ 4.87	$ 3.19	$ 2.75
Basic weighted average common shares outstanding (in shares)	76,647	83,690	88,652
Basic weighted average common units outstanding (in shares)	76,647	83,690	88,652
Diluted weighted average common shares and common share equivalents outstanding (in shares)	77,243	84,234	89,071
Diluted weighted average common units and common unit equivalents outstanding (in shares)	77,243	84,234	89,071