Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Tenant and other receivables, allowance (in dollars)	$ 18,068	$ 17,325
Deferred rents receivable, allowance (in dollars)	27,411	30,333
Debt and preferred equity investments, discount (in dollars)	19,172	18,593
Debt and preferred equity investments, allowance (in dollars)	0	1,000
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 (shares)	160,000,000	160,000,000
Common stock, shares issued (shares)	100,928,000	98,563,000
Common stock, shares outstanding (shares)	100,928,000	98,563,000
Treasury stock, shares (shares)	3,603,000	3,570,000
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 (shares)	9,200,000	9,200,000
Preferred stock, shares outstanding (shares)	9,200,000	9,200,000
SL Green Operating Partnership
Tenant and other receivables, allowance (in dollars)	18,068	17,325
Deferred rents receivable, allowance (in dollars)	27,411	30,333
Debt and preferred equity investments, discount (in dollars)	19,172	18,593
Debt and preferred equity investments, allowance (in dollars)	$ 0	$ 1,000
SL Green partner's capital, general partner common units outstanding (shares)	1,013,000	979,000
SL Green partners' capital, limited partner common units outstanding (shares)	96,312,000	94,014,000
Limited partner interests in Operating Partnership, limited partner common units outstanding (shares)	3,973,000	2,902,000
SL Green Operating Partnership | Series I Preferred Stock
Preferred Units, shares issued (shares)	9,200,000	9,200,000
Preferred Units, shares outstanding (shares)	9,200,000	9,200,000
Preferred Units, liquidation preference (in dollars per share)	$ 25.00	$ 25.00
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01