Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
ASSETS
Land and improvements	$ 1,202,872	$ 1,166,409
Buildings and tenant improvements	4,766,793	5,396,339
Construction in progress	44,259	61,205
Investments in and advances to unconsolidated companies	364,859	367,445
Undeveloped land	622,635	625,353
Real estate investment property, at cost, total	7,001,418	7,616,751
Accumulated depreciation	(1,108,650)	(1,290,417)
Net real estate investments	5,892,768	6,326,334
Real estate investments and related assets held-for-sale	55,580	394,287
Cash and cash equivalents	213,826	18,419
Accounts receivable, net of allowance of $3,597 and $2,945	22,255	22,588
Straight-line rent receivable, net of allowance of $7,447 and $7,260	105,900	125,185
Receivables on construction contracts, including retentions	40,247	7,408
Deferred financing costs, net of accumulated amortization of $59,109 and $46,407	42,268	46,317
Deferred leasing and other costs, net of accumulated amortization of $292,334 and $269,000	460,881	517,934
Escrow deposits and other assets	170,257	185,652
Assets, total	7,003,982	7,644,124
LIABILITIES AND EQUITY
Secured debt	1,173,233	1,065,628
Unsecured notes	2,616,063	2,948,405
Unsecured lines of credit	20,293	193,046
Long-term debt, total	3,809,589	4,207,079
Liabilities related to real estate investments held-for-sale	975	14,732
Construction payables and amounts due subcontractors, including retentions	55,775	44,782
Accrued real estate taxes	69,272	83,615
Accrued interest	58,904	62,407
Other accrued expenses	59,795	61,354
Other liabilities	131,735	129,860
Tenant security deposits and prepaid rents	38,355	50,450
Total liabilities	4,224,400	4,654,279
Partners' equity:
Common equity (252,927 and 252,195 General Partner Units issued and outstanding)	1,923,886	2,046,617
Preferred equity (3,176 and 3,618 Preferred Units issued and outstanding)	793,910	904,540
Total General Partner's equity	2,717,796	2,951,157
Limited Partners' common equity (6,945 and 5,231 Limited Partner Units issued and outstanding)	56,254	34,894
Accumulated other comprehensive income (loss)	987	(1,432)
Total partners' equity	2,775,037	2,984,619
Noncontrolling interests	4,545	5,226
Total equity	2,779,582	2,989,845
Liabilities and partners' equity, total	$ 7,003,982	$ 7,644,124