Consolidated Statement of Capital (Unaudited) shares in Thousands, $ in Thousands	9 Months Ended
	Sep. 30, 2017 USD ($) shares
Increase (Decrease) in Partner's Capital
DRSPP proceeds	$ 185
Conversion of common units	15,353
Reallocation of noncontrolling interests in the operating partnership	2,669
Equity component of repurchased exchangeable senior notes	(27,969)
Deferred compensation plan and stock awards, net	(1,959)
Amortization of deferred compensation plan	22,014
Repurchases of common stock	(349,991)
Contribution to consolidated joint venture interests	33,202
Deconsolidation of partially owned entity	(30,203)
Cash distributions to noncontrolling interests	$ (45,089)
Common Stock
Increase (Decrease) in Partner's Capital
DRSPP proceeds (in shares) | shares	2
Conversion of common units	$ 1
Deferred compensation plan and stock awards, net (in shares) | shares	(6)
Repurchases of common stock (in shares) | shares	(3,400)
Repurchases of common stock	$ (34)
Contributions - proceeds from stock options exercised (in shares) | shares	146
Noncontrolling Interests
Increase (Decrease) in Partner's Capital
Contribution to consolidated joint venture interests	$ 33,202
Deconsolidation of partially owned entity	(30,203)
Cash distributions to noncontrolling interests	(45,089)
SL Green Operating Partnership
Increase (Decrease) in Partner's Capital
Beginning Balance	7,750,911
Net income (loss)	51,476
Other comprehensive loss	(7,952)
Preferred distributions	(11,213)
DRSPP proceeds	185
Conversion of common units	15,353
Reallocation of noncontrolling interests in the operating partnership	2,669
Equity component of repurchased exchangeable senior notes	(27,969)
Deferred compensation plan and stock awards, net	(1,959)
Amortization of deferred compensation plan	22,014
Repurchases of common stock	(349,991)
Contribution to consolidated joint venture interests	33,202
Deconsolidation of partially owned entity	(30,203)
Contributions - proceeds from stock options exercised	12,290
Cash distributions to noncontrolling interests	(45,089)
Cash distributions declared ($2.325 per common unit, none of which represented a return of capital for federal income tax purposes)	(229,672)
Ending Balance	7,184,052
SL Green Operating Partnership | Preferred Units
Increase (Decrease) in Partner's Capital
Beginning Balance	221,932
Ending Balance	221,932
SL Green Operating Partnership | Common Stock | Partners' Interest
Increase (Decrease) in Partner's Capital
Beginning Balance	$ 7,080,406
Beginning Balance (units) | shares	100,562
Net income (loss)	$ 69,655
Preferred distributions	$ (11,213)
DRSPP proceeds (in shares) | shares	2
DRSPP proceeds	$ 185
Conversion of common units (in shares) | shares	142
Conversion of common units	$ 15,353
Reallocation of noncontrolling interests in the operating partnership	2,669
Equity component of repurchased exchangeable senior notes	$ (27,969)
Deferred compensation plan and stock awards, net (in shares) | shares	(6)
Deferred compensation plan and stock awards, net	$ (1,959)
Amortization of deferred compensation plan	$ 22,014
Repurchases of common stock (in shares) | shares	(3,400)
Repurchases of common stock	$ (349,991)
Contributions - proceeds from stock options exercised (in shares) | shares	146
Contributions - proceeds from stock options exercised	$ 12,290
Cash distributions declared ($2.325 per common unit, none of which represented a return of capital for federal income tax purposes)	(229,672)
Ending Balance	$ 6,581,768
Ending Balance (units) | shares	97,446
SL Green Operating Partnership | Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Partner's Capital
Beginning Balance	$ 22,137
Other comprehensive loss	(7,952)
Ending Balance	14,185
SL Green Operating Partnership | Noncontrolling Interests
Increase (Decrease) in Partner's Capital
Beginning Balance	426,436
Net income (loss)	(18,179)
Contribution to consolidated joint venture interests	33,202
Deconsolidation of partially owned entity	(30,203)
Cash distributions to noncontrolling interests	(45,089)
Ending Balance	$ 366,167