Investments in Unconsolidated Joint Ventures (Details 3) (USD $)	3 Months Ended		9 Months Ended			1 Months Ended	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Jun. 30, 2012 717 Fifth Avenue	Sep. 30, 2013 Joint venture	Sep. 30, 2012 Joint venture	Sep. 30, 2013 Joint venture	Sep. 30, 2012 Joint venture	Dec. 31, 2012 Joint venture	Sep. 30, 2013 Joint venture	Dec. 31, 2012 Joint venture
Assets
Commercial real estate property, net	$ 10,139,703,000		$ 10,139,703,000		$ 10,269,630,000		$ 6,566,636,000		$ 6,566,636,000		$ 6,910,991,000
Other assets	729,426,000		729,426,000		718,326,000		937,469,000		937,469,000		728,113,000
Total assets							7,504,105,000		7,504,105,000		7,639,104,000
Liabilities and members' equity
Mortgages and other loans payable	4,641,758,000		4,641,758,000		4,615,464,000		5,098,203,000		5,098,203,000		5,358,048,000	5,098,203,000	5,358,048,000
Other liabilities							378,752,000		378,752,000		406,929,000
Members' equity							2,027,150,000		2,027,150,000		1,874,127,000
Total liabilities and members equity							7,504,105,000		7,504,105,000		7,639,104,000
Company's net investment in unconsolidated joint ventures	1,109,815,000		1,109,815,000		1,032,243,000		1,109,815,000		1,109,815,000		1,032,243,000
Combined statements of income for the unconsolidated joint ventures
Total revenues							156,571,000	120,121,000	462,776,000	364,587,000
Operating expense	77,272,000	82,351,000	218,901,000	221,670,000			29,211,000	17,984,000	86,027,000	50,957,000
Ground rent	10,127,000	8,874,000	29,767,000	26,570,000			657,000	657,000	1,972,000	2,317,000
Real estate taxes	55,511,000	53,293,000	161,625,000	156,746,000			19,105,000	12,008,000	53,368,000	37,865,000
Interest expense, net of interest income	82,973,000	85,659,000	247,420,000	247,789,000			56,169,000	55,058,000	169,137,000	160,528,000
Amortization of deferred financing costs	4,331,000	4,493,000	13,034,000	11,626,000			2,869,000	2,338,000	12,454,000	7,009,000
Depreciation and amortization			264,833,000	249,950,000			49,402,000	35,242,000	144,552,000	107,749,000
Transaction related costs, net of recoveries	(2,349,000)	1,372,000	719,000	4,398,000			0	934,000	0	1,292,000
Total expenses	336,207,000	338,420,000	983,503,000	964,398,000			157,413,000	124,221,000	467,510,000	367,717,000
Loss on early extinguishment of debt	0	0	(18,523,000)	0			0	21,421,000	0	21,421,000
Net (loss) income							(842,000)	17,321,000	(4,734,000)	18,291,000
Company's equity in net income (loss) of unconsolidated joint ventures	2,939,000	11,658,000	4,251,000	80,988,000			2,939,000	11,658,000	4,251,000	80,988,000
Additional cash income recognized due to distribution of refinancing proceeds						$ 67,900,000