Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Commercial real estate properties, at cost:
Land and land interests	$ 3,844,518	$ 3,032,526
Building and improvements	8,778,593	7,884,663
Building leasehold and improvements	1,418,585	1,366,281
Properties under capital lease	27,445	50,310
Total commercial real estate properties, at cost	14,069,141	12,333,780
Less: accumulated depreciation	(1,905,165)	(1,646,240)
Total commercial real estate properties, net	12,163,976	10,687,540
Assets held for sale	462,430	0
Cash and cash equivalents	281,409	206,692
Restricted cash	149,176	142,051
Investment in marketable securities	39,429	32,049
Tenant and other receivables, net of allowance of $18,068 and $17,325 in 2014 and 2013, respectively	57,369	60,393
Related party receivables	11,735	8,530
Deferred rents receivable, net of allowance of $27,411 and $30,333 in 2014 and 2013, respectively	374,944	386,508
Debt and preferred equity investments, net of discounts and deferred origination fees of $19,172 and $18,593 in 2014 and 2013, respectively, and allowance of $1,000 in 2013	1,408,804	1,304,839
Investments in unconsolidated joint ventures	1,172,020	1,113,218
Deferred costs, net	327,962	267,058
Other assets	647,333	750,123
Total assets	17,096,587	14,959,001
Liabilities
Mortgages and other loans payable	5,586,709	4,860,578
Revolving credit facility	385,000	220,000
Term loan and senior unsecured notes	2,107,078	1,739,330
Accrued interest payable and other liabilities	137,634	114,622
Accounts payable and accrued expenses	173,246	145,889
Deferred revenue	187,148	263,261
Capitalized lease obligations	20,822	47,671
Deferred land leases payable	1,215	22,185
Dividend and distributions payable	64,393	52,255
Security deposits	66,614	61,308
Liabilities related to assets held for sale	266,873	0
Junior subordinate deferrable interest debentures held by trusts that issued trust preferred securities	100,000	100,000
Total liabilities	9,096,732	7,627,099
Commitments and contingencies	0	0
Noncontrolling interests in Operating Partnership	469,524	265,476
Preferred Units	71,115	49,550
Equity
Common stock, $0.01 par value, 160,000 shares authorized and 100,928 and 98,563 issued and outstanding at December 31, 2014 and 2013, respectively (including 3,603 and 3,570 shares held in Treasury at December 31, 2014 and 2013, respectively)	1,010	986
Additional paid-in-capital	5,289,479	5,015,904
Treasury stock at cost	(320,471)	(317,356)
Accumulated other comprehensive loss	(6,980)	(15,211)
Retained earnings	1,752,404	1,619,150
Total SL Green stockholders' equity	6,937,374	6,525,405
Noncontrolling interests in other partnerships	521,842	491,471
Total equity	7,459,216	7,016,876
Total liabilities and equity	17,096,587	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 December 31, 2014 and 2013, respectively	221,932	221,932
SL Green Operating Partnership
Commercial real estate properties, at cost:
Land and land interests	3,844,518	3,032,526
Building and improvements	8,778,593	7,884,663
Building leasehold and improvements	1,418,585	1,366,281
Properties under capital lease	27,445	50,310
Total commercial real estate properties, at cost	14,069,141	12,333,780
Less: accumulated depreciation	(1,905,165)	(1,646,240)
Total commercial real estate properties, net	12,163,976	10,687,540
Assets held for sale	462,430	0
Cash and cash equivalents	281,409	206,692
Restricted cash	149,176	142,051
Investment in marketable securities	39,429	32,049
Tenant and other receivables, net of allowance of $18,068 and $17,325 in 2014 and 2013, respectively	57,369	60,393
Related party receivables	11,735	8,530
Deferred rents receivable, net of allowance of $27,411 and $30,333 in 2014 and 2013, respectively	374,944	386,508
Debt and preferred equity investments, net of discounts and deferred origination fees of $19,172 and $18,593 in 2014 and 2013, respectively, and allowance of $1,000 in 2013	1,408,804	1,304,839
Investments in unconsolidated joint ventures	1,172,020	1,113,218
Deferred costs, net	327,962	267,058
Other assets	647,333	750,123
Total assets	17,096,587	14,959,001
Liabilities
Mortgages and other loans payable	5,586,709	4,860,578
Revolving credit facility	385,000	220,000
Term loan and senior unsecured notes	2,107,078	1,739,330
Accrued interest payable and other liabilities	137,634	114,622
Accounts payable and accrued expenses	173,246	145,889
Deferred revenue	187,148	263,261
Capitalized lease obligations	20,822	47,671
Deferred land leases payable	1,215	22,185
Dividend and distributions payable	64,393	52,255
Security deposits	66,614	61,308
Liabilities related to assets held for sale	266,873	0
Junior subordinate deferrable interest debentures held by trusts that issued trust preferred securities	100,000	100,000
Total liabilities	9,096,732	7,627,099
Commitments and contingencies	0	0
Preferred Units	71,115	49,550
Equity
Accumulated other comprehensive loss	(7,256)	(15,662)
Total liabilities and equity	17,096,587	14,959,001
SL Green stockholders equity:
SL Green partners' capital (1,013 and 979 general partner common units and 96,312 and 94,014 limited partner common units outstanding at December 31, 2014 and 2013, respectively)	7,078,924	6,506,747
Limited partner interests in SLGOP (3,973 and 2,902 limited partner common units outstanding at December 31, 2014 and 2013, respectively	113,298	77,864
Total SLGOP partners' capital	7,406,898	6,790,881
Noncontrolling interests in other partnerships	521,842	491,471
Total capital	7,928,740	7,282,352
SL Green Operating Partnership | Series I Preferred Stock
SL Green stockholders equity:
Series I Preferred Units, $25.00 liquidation preference, 9,200 issued and outstanding at both December 31, 2014 and 2013	221,932	221,932
Total capital	$ 221,932	$ 221,932