Consolidated Statements of Cash Flows (USD $) In Thousands	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010
Cash flows from operating activities:
Net income (loss)	$ 50,931	$ (17,992)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation of buildings and tenant improvements	135,809	130,236
Amortization of deferred leasing and other costs	59,285	35,937
Amortization of deferred financing costs	7,351	7,092
Straight-line rent adjustment	(11,887)	(9,083)
Impairment charges		7,974
Loss on debt extinguishment		16,127
Earnings from land and depreciated property sales	(82,664)	(19,898)
Third-party construction contracts, net	(25,658)	(17,407)
Other accrued revenues and expenses, net	263	12,815
Operating distributions received in excess of equity in earnings from unconsolidated companies	10,862	2,597
Net cash provided by operating activities	144,292	148,398
Cash flows from investing activities:
Development of real estate investments	(78,645)	(56,762)
Acquisition of real estate investments and related intangible assets, net of cash acquired	(99,817)	(19,205)
Acquisition of undeveloped land		(4,706)
Second generation tenant improvements, leasing costs and building improvements	(41,284)	(34,805)
Other deferred leasing costs	(13,807)	(16,752)
Other assets	3,149	(28,699)
Proceeds from land and depreciated property sales, net	498,249	151,835
Capital distributions from unconsolidated companies	54,730	3,897
Capital contributions and advances to unconsolidated companies, net	(16,917)	(16,577)
Net cash provided by (used for) investing activities	305,658	(21,774)
Cash flows from financing activities:
Proceeds from issuance of common shares, net		298,148
Payments for repurchases of preferred shares	(2,096)	(58,304)
Proceeds from unsecured debt issuance		250,000
Payments on and repurchases of unsecured debt	(43,377)	(387,860)
Proceeds from secured debt financings		4,160
Payments on secured indebtedness including principal amortization	(7,968)	(5,317)
Borrowings (payments) on lines of credit, net	(174,717)	313
Distributions to common shareholders	(85,843)	(76,259)
Distributions to preferred shareholders	(31,948)	(36,726)
Distributions to noncontrolling interests	(2,398)	(3,866)
Deferred financing costs	(2,342)	(1,970)
Net cash used for financing activities	(350,689)	(17,681)
Net increase in cash and cash equivalents	99,261	108,943
Cash and cash equivalents at beginning of period	18,384	147,322
Cash and cash equivalents at end of period	117,645	256,265
Non-cash investing and financing activities:
Assumption of indebtedness for real estate acquisitions	130,474	4,503
Contribution of properties to unconsolidated companies	52,868	7,002
Conversion of Limited Partner Units to common shares	1,235	(4,335)
Issuance of Limited Partner Units for acquisition	$ 28,357