Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013 Series H Preferred Units	Dec. 31, 2012 Series H Preferred Units	Dec. 31, 2013 Series G Preferred Units	Dec. 31, 2012 Series G Preferred Units	Dec. 31, 2012 Series C Preferred Stock	Dec. 31, 2013 Series I Preferred Stock	Dec. 31, 2012 Series I Preferred Stock	Dec. 31, 2013 SL Green Operating Partnership	Dec. 31, 2012 SL Green Operating Partnership	Dec. 31, 2013 SL Green Operating Partnership Series H Preferred Units	Dec. 31, 2012 SL Green Operating Partnership Series H Preferred Units	Dec. 31, 2013 SL Green Operating Partnership Series G Preferred Units	Dec. 31, 2012 SL Green Operating Partnership Series G Preferred Units	Dec. 31, 2012 SL Green Operating Partnership Series C Preferred Stock	Dec. 31, 2013 SL Green Operating Partnership Series I Preferred Stock	Dec. 31, 2012 SL Green Operating Partnership Series I Preferred Stock
Tenant and other receivables, allowance (in dollars)	$ 17,325	$ 14,341								$ 17,325	$ 14,341
Deferred rents receivable, allowance (in dollars)	30,333	29,580								30,333	29,580
Debt and preferred equity investments, discount (in dollars)	18,593	22,341								8,624	26,466
Debt and preferred equity investments, allowance (in dollars)	$ 1,000	$ 7,000								$ 1,000	$ 7,000
Preferred Units, shares issued (shares)			80,000	80,000	1,902,000	1,902,000						80,000	80,000	1,902,000	1,902,000	7,700,000	9,200,000	9,200,000
Preferred Units, shares outstanding (shares)			80,000	80,000	1,902,000	1,902,000						80,000	80,000	1,902,000	1,902,000	11,700,000	9,200,000	9,200,000
Preferred Units, liquidation preference (in dollars per share)			$ 25	$ 25	$ 25	$ 25						$ 25.00	$ 25.00	$ 25.00	$ 25.00	$ 25.00	$ 25.00	$ 25.00
Preferred stock, par value (in dollars per share)	$ 0.01						$ 0.01	$ 0.01	$ 0.01							$ 0.01	$ 0.01	$ 0.01
Preferred stock, liquidation preference (in dollars per share)							$ 25.00	$ 25.00	$ 25.00
Preferred stock, shares issued (shares)							7,700,000	9,200,000	9,200,000
Preferred stock, shares outstanding (shares)							7,700,000	9,200,000	9,200,000
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)	98,563,000	94,896,000
Common stock, shares outstanding (shares)	98,563,000	94,896,000
Treasury stock, shares (shares)	3,570,000	3,646,000
SL Green partner's capital, general partner common units outstanding (shares)										940,000	885,000
SL Green partners' capital, limited partner common units outstanding (shares)										94,993,000	90,310,000
Limited partner interests in Operating Partnership, limited partner common units outstanding (shares)										2,902,000	2,760,000