Investments in Unconsolidated Joint Ventures (Statements of Operations of the Joint Ventures) (Details) (USD $)	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Schedule of Equity Method Investments [Line Items]
Total revenue	$ 574,082,000		$ 466,680,000		$ 1,566,834,000		$ 1,376,448,000
Expenses
Depreciation and amortization	152,156,000		108,609,000		402,892,000		323,680,000
Total expenses	384,693,000		303,945,000		1,071,881,000		895,990,000
Operating income	189,389,000		162,735,000		494,953,000		480,458,000
Other expense
Interest expense	122,173,000		105,030,000		325,746,000		308,168,000
Losses from Early Extinguishment of Debt	(30,000)		(5,494,000)		122,000		(4,453,000)
Income from continuing operations	84,947,000		66,016,000		636,078,000		219,197,000
Net income	174,590,000		67,566,000		748,124,000		263,238,000
Income from unconsolidated joint ventures	14,736,000		9,217,000		72,240,000		42,129,000
Gains on Consolidation of Joint Ventures	1,810,000		0		(385,991,000)		0
Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Total revenue	37,983,000	[1]	135,998,000	[1]	273,464,000	[1]	431,133,000	[1]
Expenses
Operating	14,963,000		42,298,000		89,826,000		120,451,000
Depreciation and amortization	9,784,000		39,291,000		76,202,000		123,869,000
Total expenses	24,747,000		81,589,000		166,028,000		244,320,000
Operating income	13,236,000		54,409,000		107,436,000		186,813,000
Other expense
Interest expense	8,148,000		56,521,000		104,436,000		167,792,000
Losses from Early Extinguishment of Debt	0		0		(1,677,000)		0
Income from continuing operations	5,088,000		(2,112,000)		1,323,000		19,021,000
Gain on sale of real estate	12,441,000		990,000		14,207,000		990,000
Net income	17,529,000		(1,122,000)		15,530,000		20,011,000
Company's share of net income (loss)	3,149,000		(1,420,000)		1,974,000		10,591,000
Gain on sale of real estate	11,174,000		0		54,501,000		0
Basis differential	413,000		384,000		(1,213,000)		1,282,000
Elimination of inter-entity interest on partner loan	0		10,253,000		16,978,000		30,256,000
Income from unconsolidated joint ventures	14,736,000		9,217,000		72,240,000		42,129,000
Gains on Consolidation of Joint Ventures	1,810,000		0		(385,991,000)		0
Straight Line Rent Adjustments	(600,000)		(2,200,000)		7,600,000		9,300,000
Below market rent adjustments, net	(100,000)		22,100,000		33,900,000		70,600,000
Termination income							19,600,000
Company Share Of Termination Income							$ 11,800,000

[1] udes straight-line rent adjustments of $0.6 million and $2.2 million for the three months ended September 30, 2013 and 2012, respectively, and $7.6 million and $9.3 million for the nine months ended September 30, 2013 and 2012, respectively. Includes net below-market rent adjustments of $(0.1) million and $22.1 million for the three months ended September 30, 2013 and 2012, respectively, and $33.9 million and $70.6 million for the nine months ended September 30, 2013 and 2012, respectively. Total revenue for the nine months ended September 30, 2012 includes termination income totaling approximately $19.6 million (of which the Company's share is approximately $11.8 million) related to a lease termination with a tenant at 767 Fifth Avenue (the General Motors Building).On Feb