CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
CASH FLOWS FROM OPERATING ACTIVITIES:
Net Loss	$ (2,519)	$ (9,190)	$ (221,619)
Adjustments to Reconcile Net Loss to Net Cash Provided by Operating Activities:
Depreciation	100,074	95,931	104,175
Amortization of Deferred Financing Costs	3,460	3,963	3,473
Other Amortization	35,097	36,390	41,024
Impairment of Real Estate, Net	1,246	(2,661)	194,552
Provision for Bad Debt	542	1,110	1,880
Equity in Income of Joint Ventures	(1,559)	(980)	(675)
Distributions from Joint Ventures	1,580	1,033	3,032
Gain on Sale of Real Estate	(16,442)	(21,789)	(11,951)
Gain on Sale of Joint Venture Interests			(11,226)
Gain on Change in Control of Interests	(776)	(689)
Loss from Retirement of Debt	9,684	5,459	4,304
Mark-to-Market Loss on Interest Rate Protection Agreements	328	1,718	1,107
Decrease (Increase) in Tenant Accounts Receivable, Prepaid Expenses and Other Assets, Net	3,770	(2,933)	(1,580)
Increase in Deferred Rent Receivable	(3,504)	(7,733)	(7,041)
Increase (Decrease) in Accounts Payable, Accrued Expenses, Other Liabilities, Rents Received in Advance and Security Deposits	10,791	(5,684)	(9,411)
Decrease (Increase) in Restricted Cash		117	(15)
Payments of Premiums, Discounts and Prepayment Penalties Associated with Retirement of Debt	(7,065)	(6,528)	(6,840)
Cash Book Overdraft	1,715
Net Cash Provided by Operating Activities	136,422	87,534	83,189
CASH FLOWS FROM INVESTING ACTIVITIES:
Acquisitions of Real Estate	(55,508)	(5,277)	(22,408)
Additions to Investment in Real Estate and Non-Acquisition Tenant Improvements and Lease Costs	(83,222)	(85,247)	(67,328)
Net Proceeds from Sales of Investments in Real Estate	82,503	75,953	68,046
Contributions to and Investments in Joint Ventures	(190)	(155)	(777)
Distributions and Sales Proceeds from Joint Venture Interests	90	650	11,519
Repayments of Notes Receivable	14,365	10,394	1,460
Increase in Lender Escrows	(273)	(97)	(435)
Net Cash Used in Investing Activities	(42,235)	(3,779)	(9,923)
CASH FLOWS FROM FINANCING ACTIVITIES:
Debt and Equity Issuance Costs	(1,545)	(7,162)	(4,544)
Proceeds from the Issuance of Common Stock, Net of Underwriter's Discount	134,905	202,845	50,087
Repurchase and Retirement of Restricted Stock	(2,690)	(1,001)	(298)
Preferred Dividends	(23,258)	(15,254)	(19,677)
Redemption of Preferred Stock	(50,000)
Payments on Interest Rate Swap Agreement	(1,144)	(489)	(450)
Proceeds from Origination of Mortgage Loans Payable	100,599	255,900	105,580
Repayments on Mortgage and Other Loans Payable	(39,121)	(71,983)	(20,872)
Repayments of Senior Unsecured Notes	(166,153)	(234,307)	(259,018)
Proceeds from Unsecured Credit Facility	339,000	390,500	69,097
Repayments on Unsecured Credit Facility	(390,000)	(618,553)	(149,280)
Costs Associated with the Retirement of Debt			(1,008)
Net Cash Used in Financing Activities	(99,407)	(99,504)	(230,383)
Net Effect of Exchange Rate Changes on Cash and Cash Equivalents	5	(61)	137
Net Decrease in Cash and Cash Equivalents	(5,220)	(15,749)	(157,117)
Cash and Cash Equivalents, Beginning of Year	10,153	25,963	182,943
Cash and Cash Equivalents, End of Year	$ 4,938	$ 10,153	$ 25,963