Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Cash flows from operating activities:
Net loss	$ (14,564)	$ (58,749)
Adjustments to reconcile net loss to net cash provided by operating activities (including discontinued operations):
Depreciation and amortization	174,389	179,452
Provision for impairment of investment properties	23,490	31,752
Gain on sales of investment properties	(23,170)	(22,849)
Gain on extinguishment of debt	(3,879)	(15,429)
Loss on lease terminations	6,590	8,172
Amortization of loan fees, mortgage debt premium and discount on debt assumed, net	(2,633)	4,029
Equity in loss of unconsolidated joint ventures, net	5,467	6,028
Distributions on investments in unconsolidated joint ventures	4,301	1,073
Recognized gain on sale of marketable securities	(16,373)	(277)
Payment of leasing fees and inducements	(38,140)	(7,295)
Changes in accounts receivable, net	10,120	9,704
Changes in accounts payable and accrued expenses, net	7,634	(6,090)
Changes in other operating assets and liabilities, net	(630)	(6,097)
Other, net	(947)	4,963
Net cash provided by operating activities	131,655	128,387
Cash flows from investing activities:
Proceeds from sale of marketable securities	25,799	359
Changes in restricted escrows, net	21,099	(3,395)
Purchase of investment properties	0	(16,555)
Capital expenditures and tenant improvements	(26,690)	(20,205)
Proceeds from sales of investment properties	200,645	160,303
Investment in developments in progress	(285)	(2,441)
Investment in unconsolidated joint ventures	(7,859)	(9,557)
Distributions of investments in unconsolidated joint ventures	17,403	2,384
Other, net	21	214
Net cash provided by investing activities	230,133	111,107
Cash flows from financing activities:
Repayments of margin debt related to marketable securities	(7,541)	(2,073)
Proceeds from mortgages and notes payable	281,874	70,476
Principal payments on mortgages and notes payable	(765,729)	(571,147)
Proceeds from credit facility	290,000	489,764
Repayments of credit facility	(310,000)	(174,111)
Payment of loan fees and deposits, net	(7,433)	(10,836)
Settlement of co-venture obligation	(50,000)	0
Proceeds from issuance of common stock	272,081	0
Redemption of fractional shares of common stock	(1,253)	0
Distributions paid, net of DRP	(90,191)	(52,561)
Other, net	(2,182)	(2,601)
Net cash used in financing activities	(390,374)	(253,089)
Net decrease in cash and cash equivalents	(28,586)	(13,595)
Cash and cash equivalents, at beginning of period	136,009	130,213
Cash and cash equivalents, at end of period	107,423	116,618
Supplemental cash flow disclosure, including non-cash activities:
Cash paid for interest, net of interest capitalized	147,746	173,260
Distributions payable	38,200	0
Distributions reinvested	11,626	32,754
Accrued capital expenditures and tenant improvements	4,045	4,797
Developments in progress placed in service	929	25,651
Forgiveness of mortgage debt	27,449	14,438
Purchase of investment properties (after credits at closing):
Land, building and other improvements, net	0	(12,546)
Acquired lease intangibles and other assets	0	(4,547)
Acquired below market lease intangibles and other liabilities	0	(538)
Purchase of investment properties after credits at closing	0	16,555
Proceeds from sales of investment properties:
Land, building and other improvements, net	188,616	190,013
Accounts receivable, acquired lease intangibles and other assets	12,855	9,430
Accounts payable, acquired below market lease intangibles and other liabilities	(108)	(5,485)
Assumption of mortgage debt	0	(60,000)
Forgiveness of mortgage debt	(23,570)	0
Deferred gains	(318)	2,505
Gain on extinguishment of debt	0	991
Gain on sales of investment properties	23,170	22,849
Proceeds from sales of investment properties	$ 200,645	$ 160,303