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 income	$ 274,859	$ 198,383
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	332,983	330,003
Non-cash compensation expense	24,859	23,702
Income from unconsolidated joint ventures	(42,129)	(28,184)
Distributions of net cash flow from operations of unconsolidated joint ventures	32,359	27,222
Losses (gains) from investments in securities	(1,202)	481
Non-cash portion of interest expense	32,669	41,016
Settlement of accreted debt discount on repurchases of unsecured exchangeable senior notes	(68,760)
Losses from early extinguishments of debt	(1,000)
Gain on sale of real estate from discontinued operations	(36,877)
Gain on forgiveness of debt from discontinued operations	(17,807)
Change in assets and liabilities:
Cash held in escrows	7,803	(6,228)
Tenant and other receivables, net	28,680	13,097
Accrued rental income, net	(59,505)	(66,155)
Prepaid expenses and other assets	(29,900)	(66,597)
Accounts payable and accrued expenses	3,713	5,341
Accrued interest payable	31,677	27,228
Other liabilities	(6,939)	(15,664)
Tenant leasing costs	(41,797)	(40,786)
Total adjustments	188,827	244,476
Net cash provided by operating activities	463,686	442,859
Cash flows from investing activities:
Acquisitions of real estate	(688,073)	(41,100)
Construction in progress	(238,627)	(205,580)
Building and other capital improvements	(32,159)	(29,406)
Tenant improvements	(108,100)	(50,400)
Proceeds from the sale of real estate	61,963
Proceeds from land transaction		43,887
Proceeds from mortgage loan released from escrow		267,500
Deposits on real estate	(15,000)	10,000
Issuance of notes receivable, net	(1,764)	(6,375)
Capital contributions to unconsolidated joint ventures	(367)	(17,867)
Capital distributions from unconsolidated joint ventures	3,057
Investments in securities, net	(1,042)	(1,061)
Net cash used in investing activities	(1,020,112)	(30,402)
Cash flows from financing activities:
Proceeds from mortgage notes payable		1,178,306
Repayments of mortgage notes payable	(248,304)	(1,196,074)
Proceeds from unsecured senior notes	997,790
Redemption of unsecured senior notes	(225,000)
Redemption/repurchase of unsecured exchangeable senior notes	(507,434)
Deferred financing costs	(8,448)	(9,103)
Net proceeds from ATM stock issuances	247,186	439,037
Net proceeds from equity transactions	216	9,554
Redemption of preferred units	(18,329)
Dividends and distributions	(278,994)	(248,601)
Distributions to noncontrolling interest in property partnership	(2,250)	(1,500)
Net cash provided by (used in) financing activities	(43,567)	171,619
Net increase (decrease) in cash and cash equivalents	(599,993)	584,076
Cash and cash equivalents, beginning of period	1,823,208	478,948
Cash and cash equivalents, end of period	1,223,215	1,063,024
Supplemental disclosures:
Cash paid for interest	344,213	258,121
Interest capitalized	31,409	36,201
Non-cash investing and financing activities:
Additions to real estate included in accounts payable and accrued expenses	11,190	15,161
Mortgage note payable assumed in connection with the acquisition of real estate		143,900
Mortgage note payable extinguished through foreclosure	25,000
Real estate transferred upon foreclosure	8,198
Preferred units issued in connection with the acquisition of real estate	79,405
Dividends and distributions declared but not paid	93,461	83,584
Conversions of noncontrolling interests to stockholders' equity	11,236	71,181
Conversion of redeemable preferred units to common units	5,852
Issuance of restricted securities to employees and directors	$ 26,351	$ 25,087