Properties Held for Sale and Dispositions (Details) (USD $)	3 Months Ended		9 Months Ended		1 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 180 Maiden Lane	Jun. 30, 2014 2 Herald Square	Jul. 31, 2014 985-987 Third Avenue	May 31, 2014 673 First Avenue
Property Dispositions and Assets Held for Sale
Agreed sale consideration					$ 470,000,000	$ 365,000,000	$ 68,700,000	$ 145,000,000
Gain on sale of discontinued operations	29,507,000	13,787,000	144,242,000	14,900,000			29,800,000	117,600,000
Revenues
Rental revenue, net	9,504,000	23,606,000	44,676,000	73,738,000
Escalation and reimbursement revenues	(194,000)	3,748,000	4,413,000	11,459,000
Other income	0	9,000	21,000	523,000
Total revenues	9,310,000	27,363,000	49,110,000	85,720,000
Operating expenses	773,000	5,149,000	7,101,000	16,624,000
Real estate taxes	787,000	4,170,000	6,618,000	12,533,000
Ground rent	0	2,196,000	3,001,000	5,778,000
Interest expense, net of interest income	2,874,000	4,877,000	10,983,000	15,019,000
Amortization of deferred financing costs	48,000	210,000	369,000	630,000
Depreciable real estate reserves	0	0	0	2,150,000
Depreciation and amortization	678,000	3,311,000	5,434,000	13,133,000
Transaction related costs, net of recoveries	115,000	15,000	155,000	2,000
Total expenses	5,275,000	19,928,000	33,661,000	65,869,000
Net income from discontinued operations	$ 4,035,000	$ 7,435,000	$ 15,449,000	$ 19,851,000