Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Tenant and other receivables, allowance (in dollars)	$ 22,383	$ 21,652
Deferred rents receivable, allowance (in dollars)	29,508	29,580
Debt and preferred equity investments, discount and deferred origination fees (in dollars)	26,466	22,341
Debt and preferred equity investments, allowance (in dollars)	4,000	7,000
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)	95,780,000	94,896,000
Common stock, shares outstanding (in shares)	95,780,000	94,896,000
Treasury stock, shares (in shares)	3,566,000	3,646,000
Series G Preferred Units
Preferred Units, liquidation preference (in dollars per share)	$ 25.00	$ 25.00
Preferred Units, shares issued (in shares)	1,902,000	1,902,000
Preferred Units, shares outstanding (in shares)	1,902,000	1,902,000
Series H Preferred Units
Preferred Units, liquidation preference (in dollars per share)	$ 25.00	$ 25.00
Preferred Units, shares issued (in shares)	80,000	80,000
Preferred Units, shares outstanding (in shares)	80,000	80,000
Series C Preferred Units
Preferred Units, liquidation preference (in dollars per share)	$ 25.00	$ 25.00
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares issued (in shares)		7,700,000
Preferred stock, shares outstanding (in shares)		7,700,000
Series I Preferred Units
Preferred Units, liquidation preference (in dollars per share)	$ 25.00	$ 25.00
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
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
Tenant and other receivables, allowance (in dollars)	22,383	21,652
Deferred rents receivable, allowance (in dollars)	29,508	29,580
Debt and preferred equity investments, discount and deferred origination fees (in dollars)	26,466	22,341
Debt and preferred equity investments, allowance (in dollars)	$ 4,000	$ 7,000
SL Green partners' capital, general partner common units outstanding (in shares)	950,000	940,000
SL Green partners' capital, limited partner common units outstanding (in shares)	91,264,000	90,310,000
Limited partner interests in Operating Partnership, limited partner common units outstanding (in shares)	2,792,000	2,760,000
SL Green Operating Partnership | Series G Preferred Units
Preferred Units, liquidation preference (in dollars per share)	$ 25.00	$ 25.00
Preferred Units, shares issued (in shares)	1,902,000	1,902,000
Preferred Units, shares outstanding (in shares)	1,902,000	1,902,000
SL Green Operating Partnership | Series H Preferred Units
Preferred Units, liquidation preference (in dollars per share)	$ 25.00	$ 25.00
Preferred Units, shares issued (in shares)	80,000	80,000
Preferred Units, shares outstanding (in shares)	80,000	80,000
SL Green Operating Partnership | Series C Preferred Units
Preferred stock, shares issued (in shares)		7,700,000
Preferred stock, shares outstanding (in shares)		7,700,000
SL Green Operating Partnership | Series I Preferred Units
Preferred stock, shares issued (in shares)	9,200,000	9,200,000
Preferred stock, shares outstanding (in shares)	9,200,000	9,200,000