Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Cash flows from operating activities:
Net income (loss)	$ 96,309	$ 65,262	$ (271,490)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation of buildings and tenant improvements	267,222	271,058	266,803
Amortization of deferred leasing and other costs	118,457	89,126	73,323
Amortization of deferred financing costs	14,530	13,897	13,679
Straight-line rent adjustment	(23,877)	(15,233)	(18,832)
Impairment charges	12,931	9,834	302,566
(Gain) loss on debt extinguishment	0	16,349	(20,700)
(Gain) loss on acquisitions	(1,057)	(57,715)	1,062
Deferred tax asset valuation allowance	0	0	7,278
Earnings from land and depreciated property sales	(169,431)	(72,716)	(19,480)
Build- for- Sale operations, net	0	0	14,482
Third-party construction contracts, net	(17,352)	(6,449)	(4,583)
Other accrued revenues and expenses, net	24,036	68,512	48,543
Operating distributions received in excess of equity in earnings from unconsolidated companies	15,804	8,851	8,533
Net cash provided by operating activities	337,572	390,776	401,184
Cash flows from investing activities:
Development of real estate investments	(162,070)	(119,404)	(268,890)
Acquisition of real estate investments and related intangible assets, net of cash acquired	(544,816)	(488,539)	(31,658)
Acquisition of undeveloped land	(14,090)	(14,404)	(5,474)
Second generation tenant improvements, leasing costs and building improvements	(99,264)	(88,723)	(79,054)
Other deferred leasing costs	(26,311)	(38,905)	(23,329)
Other assets	747	(7,260)	(583)
Proceeds from land and depreciated property sales, net	1,572,093	499,520	256,330
Capital distributions from unconsolidated companies	59,252	22,119	0
Capital contributions and advances to unconsolidated companies, net	(34,606)	(53,194)	(23,481)
Net cash provided by (used for) investing activities	750,935	(288,790)	(176,139)
Cash flows from financing activities:
Contributions from the General Partner	0	298,066	551,136
Payments for redemption/repurchase of Preferred Units	(110,726)	(118,787)	0
Proceeds from unsecured debt issuance	0	250,000	500,000
Payments on and repurchases of unsecured debt	(334,432)	(392,597)	(707,016)
Proceeds from secured debt financings	0	4,158	290,418
Payments on secured indebtedness including principal amortization	(29,025)	(207,060)	(11,396)
Borrowings (payments) on lines of credit, net	(172,753)	177,276	(467,889)
Distributions to common unitholders	(176,593)	(165,881)	(156,357)
Distributions to preferred unitholders	(60,353)	(69,468)	(73,451)
Contributions from (distributions to) noncontrolling interests, net	(566)	(1,739)	3,443
Deferred financing costs	(8,652)	(5,074)	(28,679)
Net cash used for financing activities	(893,100)	(231,106)	(99,791)
Net increase (decrease) in cash and cash equivalents	195,407	(129,120)	125,254
Cash and cash equivalents at beginning of year	18,419	147,539	22,285
Cash and cash equivalents at end of year	213,826	18,419	147,539
Non-cash investing and financing activities:
Assumption of indebtedness and other liabilities for real estate acquisitions	177,082	527,464	0
Contribution of properties to, net of debt assumed by, unconsolidated companies	53,293	41,609	20,663
Investments and advances related to acquisition of previously unconsolidated companies	5,987	184,140	206,852
Assumption of indebtedness by buyer in real estate dispositions	24,914	0	0
Conversion of Limited Partner Units to common shares of the General Partner	3,130	(8,055)	592
Issuance of Limited Partner Units for acquisition	$ 28,357	$ 0	$ 0