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
Revenues from real estate operations received	$ 483,421	$ 476,762	$ 453,847
Construction contract and other service revenues received	77,831	88,433	112,644
Property operating expenses paid	(174,683)	(180,041)	(173,625)
Construction contract and other service expenses paid	(67,952)	(94,140)	(124,867)
General, administrative, leasing, business development and land carry costs paid	22,904	28,027	23,969
Interest expense paid	(87,394)	(93,715)	(87,917)
Previously accreted interest expense paid	0	(17,314)	0
Settlement of interest rate derivatives	(29,738)	0	0
Proceeds from sale of trading marketable securities	18,975	0	0
Exit costs on property dispositions	(4,146)	0	0
Payments in connection with early extinguishment of debt	(2,637)	(353)	0
Interest and other income received	1,073	698	323
Income taxes paid	(8)	(160)	0
Net cash provided by operating activities	191,838	152,143	156,436
Purchases of and additions to properties
Construction, development and redevelopment	(165,275)	(232,667)	(303,064)
Acquisitions of operating properties	(48,308)	(32,856)	(146,275)
Tenant improvements on operating properties	(27,103)	(37,195)	(20,826)
Other capital improvements on operating properties	(20,066)	(16,906)	(10,422)
Proceeds from sales of properties	290,603	79,638	27,576
Proceeds from sale of equity method investment	0	5,773	0
Mortgage and other loan receivables funded or acquired	(14,232)	(23,377)	(5,588)
Mortgage and other loan receivables payments received	10,113	16,759	1,568
Leasing costs paid	(13,278)	(15,997)	(14,403)
Investment in unconsolidated entities	(250)	(250)	(6,600)
Other	1,540	(3,309)	(1,133)
Net cash provided by (used in) investing activities	13,744	(260,387)	(479,167)
Proceeds from debt
Revolving Credit Facility	329,000	1,180,000	663,000
Other debt proceeds	403,117	456,206	359,912
Repayments of debt
Revolving Credit Facility	(991,000)	(813,000)	(733,000)
Scheduled principal amortization	(11,684)	(13,755)	(13,996)
Other debt repayments	(124,386)	(698,100)	(66,663)
Deferred financing costs paid	(3,371)	(13,113)	(8,570)
Net proceeds from issuance of preferred shares	165,652	0	0
Net proceeds from issuance of common shares	205,425	147,828	250,196
Redemption of preferred shares	(55,000)	0	0
Acquisition of noncontrolling interests in consolidated entities	0	0	(4,462)
Common share dividends paid	(89,161)	(114,643)	(93,792)
Preferred share dividends paid	(19,087)	(16,102)	(16,102)
Distributions paid to noncontrolling interests in the Operating Partnership	(5,828)	(7,875)	(8,099)
Restricted share redemptions	(3,379)	(3,990)	(3,913)
Other	(845)	245	60
Net cash (used in) provided by financing activities	(200,547)	103,701	324,571
Net increase (decrease) in cash and cash equivalents	5,035	(4,543)	1,840
Cash and cash equivalents
Beginning of period	5,559	10,102	8,262
End of period	10,594	5,559	10,102
Reconciliation of net income (loss) to net cash provided by operating activities:
Net income (loss)	20,341	(127,576)	45,504
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and other amortization	124,418	136,594	125,819
Impairment losses	62,702	151,021	0
Loss on interest rate derivatives	0	29,805	0
Settlement of previously accreted interest expense	0	(17,314)	0
Amortization of deferred financing costs	6,243	6,596	5,871
Increase in deferred rent receivable	(11,776)	(10,102)	(5,706)
Amortization of net debt discounts	3,155	5,540	5,841
Gain on sales of real estate	(20,961)	(7,528)	(3,917)
Gain on equity method investment	0	(2,452)	(6,406)
Share-based compensation	9,982	11,920	11,845
(Gain) loss on early extinguishment of debt	(3,430)	1,670	0
Other	(3,195)	(314)	(3,872)
Changes in operating assets and liabilities:
Decrease (increase) in accounts receivable	6,693	(7,094)	(1,680)
Decrease (increase) in restricted cash and marketable securities	14,934	2,160	(4,875)
Decrease (increase) in prepaid expenses and other assets	8,550	(687)	8,674
Increase (decrease) in accounts payable, accrued expenses and other liabilities	4,101	(18,041)	(19,644)
Decrease in rents received in advance and security deposits	(1,916)	(2,055)	(1,018)
Decrease in interest rate derivatives in connection with cash settlement	(28,003)	0	0
Net cash provided by operating activities	191,838	152,143	156,436
Supplemental schedule of non-cash investing and financing activities:
(Decrease) increase in accrued capital improvements, leasing and other investing activity costs	(1,227)	11,719	4,576
Increase in property, debt and other liabilities in connection with acquisitions	0	3,040	74,244
Decrease in property in connection with surrender of property in settlement of debt	12,042	0	0
Decrease in debt in connection with surrender of property in settlement of debt	16,304	0	0
Increase in property and noncontrolling interests in connection with property contribution by a noncontrolling interest in a joint venture	0	0	9,000
Increase (decrease) in fair value of derivatives applied to AOCL and noncontrolling interests	4,040	1,438	(1,846)
Dividends/distribution payable	28,698	35,038	32,986
Decrease in noncontrolling interests and increase in shareholders’ equity in connection with the conversion of common units into common shares	2,814	1,521	9,567
Adjustments to noncontrolling interests resulting from changes in Operating Partnership ownership	4,627	2,798	10,274
Increase in redeemable noncontrolling interest and decrease in shareholders’ equity in connection with adjustment to arrive at fair value of noncontrolling interest	$ 3,955	$ 1,315	$ 0