Investment in Unconsolidated Entities (Details 6) (USD $) In Thousands, unless otherwise specified							3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2014 Equity Method Investments Unconsolidated property interests	Dec. 31, 2013 Equity Method Investments Unconsolidated property interests	Mar. 31, 2014 Equity Method Investments Unconsolidated property interests Maximum
Assets:
Investment properties, at cost	$ 35,598,458	$ 35,126,344			$ 16,019,083	$ 15,824,689
Less - accumulated depreciation	10,309,988	10,067,743			5,339,813	5,294,578
Investment properties, net	25,288,470	25,058,601			10,679,270	10,530,111
Cash and cash equivalents	1,013,368	1,716,863	829,966	1,184,518	747,103	792,751
Tenant receivables and accrued revenue, net	530,479	581,482			287,777	310,320
Investment in unconsolidated entities, at equity					28,832	38,352
Deferred costs and other assets	1,564,988	1,519,814			520,058	586,622
Total assets					12,263,040	12,258,156
Liabilities and Partners' Deficit:
Mortgages and unsecured indebtedness	23,186,610	23,588,531			13,013,998	13,024,257
Accounts payable, accrued expenses, intangibles, and deferred revenues	1,259,452	1,374,113			977,038	849,107
Other liabilities	198,610	257,222			542,950	514,822
Total liabilities	25,783,706	26,311,457			14,533,986	14,388,186
Preferred units					67,450	67,450
Partners' deficit	(3,273,092)	(3,218,686)			(2,338,396)	(2,197,480)
Total liabilities and equity	32,755,599	33,324,574			12,263,040	12,258,156
Our Share of:
Partners' deficit					(763,064)	(717,776)
Add: Excess Investment					1,971,553	2,059,584
Our net Investment in unconsolidated entities, at equity	$ 2,347,523	$ 2,433,399			$ 1,208,489	$ 1,341,808
Life of joint ventures with excess investment							40 years