Basis of Presentation and Significant Accounting Policies (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Property Plant And Equipment [Line Items]
Impairment losses, acquisition related costs and tenant buy-outs	$ 120,786	$ 35,299	$ 109,458
Net gain on disposition of wholly owned and partially owned assets	13,347	15,134	81,432
Significant Policies Other Details [Abstract]
Accounts receivable, allowance for doubtful accounts	37,674	43,241
Receivables Arising From Straight Lining Of Rents Allowance	3,165	3,290
Condominium Assets held for sale	53,737	60,785
Income Taxes [Abstract]
Income Tax Liability Relating to Taxable REIT Subsidiaries Current	20,336	26,645
Equity Method Investments [Member]
Other Than Temporary Impairment Losses Investments Portion Recognized In Earnings Net By Investment Category [Line Items]
Other than Temporary Impairment Losses, Investments	4,936	13,794	11,481
Real Estate [Member]
Property Plant And Equipment [Line Items]
Impairment losses, acquisition related costs and tenant buy-outs	107,000	0	72,500
Cost Of Real Estate Acquisitions Not Consummated [Member]
Property Plant And Equipment [Line Items]
Impairment losses, acquisition related costs and tenant buy-outs	11,248	32,259	6,945
Development Related Real Estate [Member]
Property Plant And Equipment [Line Items]
Impairment losses, acquisition related costs and tenant buy-outs	0	3,040	0
Condominium Units [Member]
Property Plant And Equipment [Line Items]
Impairment losses, acquisition related costs and tenant buy-outs	2,538	0	30,013
Net gain on disposition of wholly owned and partially owned assets	$ 1,274	$ 5,884	$ 3,149