Investment in Unconsolidated Joint Ventures (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Assets
Commercial real estate property, net	$ 11,957,923		$ 11,957,923		$ 10,687,540
Other assets	679,840		679,840		750,123
Liabilities and members' equity
Mortgages and other loans payable	6,130,426		6,130,426		4,860,578
Company's investments in unconsolidated joint ventures	971,926		971,926		1,113,218
Combined statements of income for the unconsolidated joint ventures
Operating expenses	70,675	68,611	144,160	139,780
Ground rent	8,040	7,930	16,073	16,058
Real estate taxes	53,267	51,749	108,583	104,203
Interest expense, net of interest income	78,611	79,551	156,330	157,860
Amortization of deferred financing costs	5,500	4,229	9,357	8,681
Transaction related costs, net of recoveries	1,697	1,706	4,171	3,085
Depreciation and amortization	94,838	81,577	184,217	160,200
Total expenses	336,500	316,867	670,019	632,449
Company's equity in net income (loss) from unconsolidated joint ventures	8,619	(3,761)	14,748	1,313
Joint Venture
Assets
Commercial real estate property, net	4,925,422		4,925,422		6,846,021
Other assets	749,571		749,571		827,282
Total assets	5,674,993		5,674,993		7,673,303
Liabilities and members' equity
Mortgages and other loans payable	3,575,456		3,575,456		5,066,710
Other liabilities	485,753		485,753		596,960
Members' equity	1,613,784		1,613,784		2,009,633
Total liabilities and members' equity	5,674,993		5,674,993		7,673,303
Company's investments in unconsolidated joint ventures	971,926		971,926		1,113,218
Combined statements of income for the unconsolidated joint ventures
Total revenues	130,495	154,974	291,633	306,205
Operating expenses	18,362	28,205	45,045	56,816
Ground rent	2,632	658	4,657	1,315
Real estate taxes	15,406	16,958	32,342	34,263
Interest expense, net of interest income	44,728	56,561	97,064	112,968
Amortization of deferred financing costs	2,026	5,302	6,659	9,585
Transaction related costs, net of recoveries	(207)	0	64	0
Depreciation and amortization	33,858	52,539	79,462	95,150
Total expenses	116,805	160,223	265,293	310,097
Loss on early extinguishment of debt	(3,546)	0	(6,743)	0
Net income (loss) before gain on sale	10,144	(5,249)	19,597	(3,892)
Company's equity in net income (loss) from unconsolidated joint ventures	$ 8,619	$ (3,761)	$ 14,748	$ 1,313