Supplemental Detail for Certain Components of Consolidated Balance Sheets (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Other assets [Abstract]
Value of in-place leases, net of accumulated amortization	$ 119,934	$ 123,255
Value of above-market leases, net of accumulated amortization	29,422	30,081
Deferred bond financing costs, net	21,620	22,209
Notes receivable issued in connection with property sales	19,003	19,025
Prepaid expenses	9,415	9,833
Note receivable issued in connection with acquisitions	8,780	8,780
Credit facility origination costs, net	2,845	3,141
Loans receivable	4,704	2,554
Restricted escrow deposits	2,239	50
Corporate assets, net of accumulated depreciation and amortization	912	849
Deferred financing costs on mortgages payable, net	669	751
Other items	1,156	2,107
Other assets	220,699	222,635
Distributions payable [Abstract]
Distributions payable	22,753	21,405
Accounts payable and accrued expenses [Abstract]
Bond interest payable	12,925	35,195
Accrued costs on properties under development	7,588	4,766
Other items	13,906	18,809
Accounts payable and accrued expenses	34,419	58,770
Other liabilities disclosure [Abstract]
Rent received in advance	18,001	18,149
Value of in-place below-market leases, net of accumulated amortization	6,246	6,423
Security deposits	4,633	4,607
Other items	1,564	0
Other liabilities	30,444	29,179
Common Stock [Member]
Distributions payable [Abstract]
Distributions payable	19,452	19,384
Preferred Stock [Member]
Distributions payable [Abstract]
Distributions payable	$ 3,301	$ 2,021