Consolidated Statement of Capital shares in Thousands, $ in Thousands	6 Months Ended
	Jun. 30, 2017 USD ($) shares
Increase (Decrease) in Partner's Capital
DRSPP proceeds	$ 111
Conversion of common units	13,242
Reallocation of noncontrolling interests in the operating partnership	(12,712)
Equity component of repurchased exchangeable senior notes	(18,824)
Deferred compensation plan and stock award, net	(1,943)
Amortization of deferred compensation plan	15,487
Repurchase of common stock	(253,197)
Contribution to consolidated joint venture interests	33,009
Deconsolidation of partially owned entity	(30,203)
Cash distributions to noncontrolling interests	$ (609)
Common Stock
Increase (Decrease) in Partner's Capital
DRSPP proceeds (in shares) | shares	1
Conversion of common units	$ 1
Deferred compensation plan and stock award, net (in shares) | shares	(8)
Repurchase of common stock (in shares) | shares	(2,448)
Repurchase of common stock	$ (24)
Contributions - proceeds from stock options exercised (in shares) | shares	138
Noncontrolling Interests
Increase (Decrease) in Partner's Capital
Contribution to consolidated joint venture interests	$ 33,009
Deconsolidation of partially owned entity	(30,203)
Cash distributions to noncontrolling interests	(609)
SL Green Operating Partnership
Increase (Decrease) in Partner's Capital
Beginning Balance	7,750,911
Net income (loss)	10,343
Other comprehensive loss	(7,783)
Preferred distributions	(7,475)
DRSPP proceeds	111
Conversion of common units	13,242
Reallocation of noncontrolling interests in the operating partnership	(12,712)
Equity component of repurchased exchangeable senior notes	(18,824)
Deferred compensation plan and stock award, net	(1,943)
Amortization of deferred compensation plan	15,487
Repurchase of common stock	(253,197)
Contribution to consolidated joint venture interests	33,009
Deconsolidation of partially owned entity	(30,203)
Contributions - proceeds from stock options exercised	11,595
Cash distributions to noncontrolling interests	(609)
Cash distributions declared ($1.55 per common unit, none of which represented a return of capital for federal income tax purposes)	(154,312)
Ending Balance	7,347,640
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)	$ 27,048
Preferred distributions	$ (7,475)
DRSPP proceeds (in shares) | shares	1
DRSPP proceeds	$ 111
Conversion of common units (in shares) | shares	122
Conversion of common units	$ 13,242
Reallocation of noncontrolling interests in the operating partnership	(12,712)
Equity component of repurchased exchangeable senior notes	$ (18,824)
Deferred compensation plan and stock award, net (in shares) | shares	(8)
Deferred compensation plan and stock award, net	$ (1,943)
Amortization of deferred compensation plan	$ 15,487
Repurchase of common stock (in shares) | shares	(2,448)
Repurchase of common stock	$ (253,197)
Contributions - proceeds from stock options exercised (in shares) | shares	138
Contributions - proceeds from stock options exercised	$ 11,595
Cash distributions declared ($1.55 per common unit, none of which represented a return of capital for federal income tax purposes)	(154,312)
Ending Balance	$ 6,699,426
Ending Balance (units) | shares	98,367
SL Green Operating Partnership | Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Partner's Capital
Beginning Balance	$ 22,137
Other comprehensive loss	(7,783)
Ending Balance	14,354
SL Green Operating Partnership | Noncontrolling Interests
Increase (Decrease) in Partner's Capital
Beginning Balance	426,436
Net income (loss)	(16,705)
Contribution to consolidated joint venture interests	33,009
Deconsolidation of partially owned entity	(30,203)
Cash distributions to noncontrolling interests	(609)
Ending Balance	$ 411,928