Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Debt and preferred equity investments, discount and deferred origination fees	$ 6,494	$ 11,232
Allowance for loan and lease losses, real estate	$ 6,630	$ 13,213
Preferred stock, par value (in dollars per share)	$ 0.01
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	160,000,000	160,000,000
Common stock, shares issued (in shares)	67,926,000	69,534,000
Common stock, shares outstanding (in shares)	67,926,000	69,534,000
Treasury stock, shares (in shares)	1,061,000	1,026,000
Land and land interests	$ 1,489,101	$ 1,315,832
Building and improvements	3,828,052	4,168,193
Building leasehold and improvements	1,649,796	1,448,134
Right of use asset - financing leases	27,445	55,711
Accumulated depreciation	1,904,465	1,956,077
Other assets	347,407	448,213
Mortgages and other loans payable, net	1,422,287	1,979,972
Accrued interest payable	20,777	14,825
Lease liability - financing leases	125,168	152,521
Other liabilities	$ 157,375	$ 302,798
Series I Preferred Stock
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, liquidation preference (in dollars per share)	$ 25.00	$ 25.00
Preferred stock, shares issued (in shares)	9,200,000	9,200,000
Preferred stock, shares outstanding (in shares)	9,200,000	9,200,000
SL Green Operating Partnership
Debt and preferred equity investments, discount and deferred origination fees	$ 6,494	$ 11,232
Allowance for loan and lease losses, real estate	$ 6,630	$ 13,213
Limited partner interests in Operating Partnership, limited partner common units outstanding (shares)	3,888,000	3,939,000
SL Green partner's capital, general partner common units outstanding (shares)	707,000	724,000
SL Green partners' capital, limited partner common units outstanding (shares)	66,158,000	67,784,000
Land and land interests	$ 1,489,101	$ 1,315,832
Building and improvements	3,828,052	4,168,193
Building leasehold and improvements	1,649,796	1,448,134
Right of use asset - financing leases	27,445	55,711
Accumulated depreciation	1,904,465	1,956,077
Other assets	347,407	448,213
Mortgages and other loans payable, net	1,422,287	1,979,972
Accrued interest payable	20,777	14,825
Lease liability - financing leases	125,168	152,521
Other liabilities	$ 157,375	$ 302,798
SL Green Operating Partnership | Series I Preferred Stock
Preferred units, liquidation preference (in dollars per share)	$ 25.00	$ 25.00
Preferred units, shares issued (in shares)	9,200,000	9,200,000
Preferred units, shares outstanding (in shares)	9,200,000	9,200,000
Variable Interest Entity, Primary Beneficiary
Land and land interests	$ 316,000	$ 41,200
Building and improvements	341,200	57,900
Building leasehold and improvements	2,000	2,000
Right of use asset - financing leases	53,200	37,800
Accumulated depreciation	18,500	10,300
Other assets	293,800	289,500
Mortgages and other loans payable, net	450,100	94,000
Accrued interest payable	1,300	700
Lease liability - financing leases	45,400	29,900
Other liabilities	$ 24,900	$ 56,600