Consolidated Statements of Cash Flows (USD $) In Thousands	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010
Cash flows from operating activities:
Net income	$ 36,062	$ 39,443
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation of buildings and tenant improvements	204,134	201,352
Amortization of deferred leasing and other costs	88,295	62,734
Amortization of deferred financing costs	11,070	10,492
Straight-line rent adjustment	(19,012)	(12,252)
Impairment charges	0	9,834
Loss on debt extinguishment	0	16,294
Gain on acquisitions, net	0	(57,815)
Earnings from land and depreciated property sales	(83,315)	(31,300)
Third-party construction contracts, net	(18,417)	(16,872)
Other accrued revenues and expenses, net	14,586	13,293
Operating distributions received in excess of equity in earnings from unconsolidated companies	11,681	7,649
Net cash provided by operating activities	245,084	242,852
Cash flows from investing activities:
Development of real estate investments	(125,676)	(82,372)
Acquisition of real estate investments and related intangible assets, net of cash acquired	(179,047)	(260,877)
Acquisition of undeveloped land	(3,825)	(13,384)
Second generation tenant improvements, leasing costs and building improvements	(71,732)	(63,361)
Other deferred leasing costs	(20,950)	(26,060)
Other assets	(4,500)	(16,847)
Proceeds from land and depreciated property sales, net	504,688	200,445
Capital distributions from unconsolidated companies	54,730	3,897
Capital contributions and advances to unconsolidated companies, net	(28,362)	(48,410)
Net cash provided by (used for) investing activities	125,326	(306,969)
Cash flows from financing activities:
Proceeds from issuance of common shares, net	0	297,896
Payments for redemption/repurchase of preferred shares	(110,726)	(115,849)
Proceeds from unsecured debt issuance	0	250,000
Payments on and repurchases of unsecured debt	(166,346)	(392,181)
Proceeds from secured debt financings	0	3,987
Payments on secured indebtedness including principal amortization	(24,841)	(8,814)
Borrowings on lines of credit, net	111,247	82,210
Distributions to common shareholders	(128,817)	(119,116)
Distributions to preferred shareholders	(46,347)	(53,452)
Distributions to noncontrolling interests	(3,952)	(4,844)
Deferred financing costs	(2,830)	(2,193)
Net cash used for financing activities	(372,612)	(62,356)
Net decrease in cash and cash equivalents	(2,202)	(126,473)
Cash and cash equivalents at beginning of period	18,384	147,322
Cash and cash equivalents at end of period	16,182	20,849
Non-cash investing and financing activities:
Assumption of indebtedness and other liabilities in real estate acquisitions	150,042	332,982
Contribution of properties to unconsolidated companies	53,245	7,002
Investment and advances related to acquisition of previously unconsolidated companies	5,987	134,026
Issuance of Limited Partner Units for acquisition	28,357	0
Parent [Member]
Non-cash investing and financing activities:
Conversion of Limited Partner Units to common shares	$ 3,052	$ (7,829)