Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Commercial real estate properties, at cost:
Land and land interests	$ 3,833,305	$ 3,032,526
Building and improvements	8,679,637	7,884,663
Building leasehold and improvements	1,405,255	1,366,281
Properties under capital lease	27,445	50,310
Total commercial real estate properties, at cost	13,945,642	12,333,780
Less: accumulated depreciation	(1,826,027)	(1,646,240)
Total commercial real estate properties, net	12,119,615	10,687,540
Assets held for sale	753,457	0
Cash and cash equivalents	253,520	206,692
Restricted cash	159,303	142,051
Investment in marketable securities	39,293	32,049
Tenant and other receivables, net of allowance of $20,719 and $17,325 in 2014 and 2013, respectively	64,184	60,393
Related party receivables	13,262	8,530
Deferred rents receivable, net of allowance of $27,185 and $30,333 in 2014 and 2013, respectively	364,284	386,508
Debt and preferred equity investments, net of discounts and deferred origination fees of $19,801 and $18,593 in 2014 and 2013, respectively, and allowance of $1,000 in 2013	1,432,951	1,304,839
Investments in unconsolidated joint ventures	996,842	1,113,218
Deferred costs, net	310,860	267,058
Other assets	729,538	750,123
Total assets	17,237,109	14,959,001
Liabilities
Mortgages and other loans payable	5,890,782	4,860,578
Revolving credit facility	244,000	220,000
Term loan and senior unsecured notes	2,054,168	1,739,330
Accrued interest payable and other liabilities	127,811	114,622
Accounts payable and accrued expenses	183,001	145,889
Deferred revenue	215,527	263,261
Capitalized lease obligations	20,728	47,671
Deferred land leases payable	1,129	22,185
Dividend and distributions payable	53,571	52,255
Security deposits	66,659	61,308
Liabilities related to assets held for sale	461,891	0
Junior subordinated deferrable interest debentures held by trusts that issued trust preferred securities	100,000	100,000
Total liabilities	9,419,267	7,627,099
Commitments and contingencies
Noncontrolling interests in the Operating Partnership	381,274	265,476
Preferred Units	73,115	49,550
Equity
Common stock, $0.01 par value, 160,000 shares authorized and 99,547 and 98,563 issued and outstanding at September 30, 2014 and December 31, 2013, respectively (including 3,602 and 3,570 shares held in Treasury at September 30, 2014 and December 31, 2013, respectively)	996	986
Additional paid-in-capital	5,130,858	5,015,904
Treasury stock at cost	(320,222)	(317,356)
Accumulated other comprehensive loss	(2,896)	(15,211)
Retained earnings	1,813,956	1,619,150
Total SL Green stockholders' equity	6,844,624	6,525,405
Noncontrolling interests in other partnerships	518,829	491,471
Total equity	7,363,453	7,016,876
Total liabilities and equity	17,237,109	14,959,001
Series I Preferred Stock
Equity
Series I Preferred Stock, $0.01 par value, $25.00 liquidation preference, 9,200 issued and outstanding at both September 30, 2014 and December 31, 2013	221,932	221,932
SL Green Operating Partnership
Commercial real estate properties, at cost:
Land and land interests	3,833,305	3,032,526
Building and improvements	8,679,637	7,884,663
Building leasehold and improvements	1,405,255	1,366,281
Properties under capital lease	27,445	50,310
Total commercial real estate properties, at cost	13,945,642	12,333,780
Less: accumulated depreciation	(1,826,027)	(1,646,240)
Total commercial real estate properties, net	12,119,615	10,687,540
Assets held for sale	753,457	0
Cash and cash equivalents	253,520	206,692
Restricted cash	159,303	142,051
Investment in marketable securities	39,293	32,049
Tenant and other receivables, net of allowance of $20,719 and $17,325 in 2014 and 2013, respectively	64,184	60,393
Related party receivables	13,262	8,530
Deferred rents receivable, net of allowance of $27,185 and $30,333 in 2014 and 2013, respectively	364,284	386,508
Debt and preferred equity investments, net of discounts and deferred origination fees of $19,801 and $18,593 in 2014 and 2013, respectively, and allowance of $1,000 in 2013	1,432,951	1,304,839
Investments in unconsolidated joint ventures	996,842	1,113,218
Deferred costs, net	310,860	267,058
Other assets	729,538	750,123
Total assets	17,237,109	14,959,001
Liabilities
Mortgages and other loans payable	5,890,782	4,860,578
Revolving credit facility	244,000	220,000
Term loan and senior unsecured notes	2,054,168	1,739,330
Accrued interest payable and other liabilities	127,811	114,622
Accounts payable and accrued expenses	183,001	145,889
Deferred revenue	215,527	263,261
Capitalized lease obligations	20,728	47,671
Deferred land leases payable	1,129	22,185
Dividend and distributions payable	53,571	52,255
Security deposits	66,659	61,308
Liabilities related to assets held for sale	461,891	0
Junior subordinated deferrable interest debentures held by trusts that issued trust preferred securities	100,000	100,000
Total liabilities	9,419,267	7,627,099
Commitments and contingencies
Preferred Units	73,115	49,550
Equity
Accumulated other comprehensive loss	(3,000)	(15,662)
Total liabilities and equity	17,237,109	14,959,001
SLGOP partners' capital:
SL Green partners' capital 997 and 979 general partner common units and 94,948 and 94,014 limited partner common units outstanding at September 30, 2014 and December 31, 2013, respectively)	6,922,104	6,506,747
Limited partner interests in SLGOP (3,735 and 2,902 limited partner common units outstanding at September 30, 2014 and December 31, 2013, respectively)	84,862	77,864
Total SLGOP partners' capital	7,225,898	6,790,881
Noncontrolling interests in other partnerships	518,829	491,471
Total capital	7,744,727	7,282,352
SL Green Operating Partnership | Series I Preferred Stock
SLGOP partners' capital:
Series I Preferred Units, $25.00 liquidation preference, 9,200 outstanding at both September 30, 2014 and December 31, 2013	221,932	221,932
Total capital	$ 221,932	$ 221,932