Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
ASSETS
Land and improvements	$ 1,209,840	$ 1,202,872
Buildings and tenant improvements	4,868,066	4,766,793
Construction in progress	80,306	44,259
Investments in and advances to unconsolidated companies	361,818	364,859
Undeveloped land	622,642	622,635
Real estate investment property, at cost, total	7,142,672	7,001,418
Accumulated depreciation	(1,151,322)	(1,108,650)
Net real estate investments	5,991,350	5,892,768
Real estate investments and other assets held-for-sale	19,395	55,580
Cash and cash equivalents	14,740	213,826
Accounts receivable, net of allowance of $2,693 and $3,597	24,045	22,255
Straight-line rent receivable, net of allowance of $6,997 and $7,447	111,115	105,900
Receivables on construction contracts, including retentions	33,257	40,247
Deferred financing costs, net of accumulated amortization of $42,720 and $59,109	39,685	42,268
Deferred leasing and other costs, net of accumulated amortization of $311,525 and $292,334	469,936	460,881
Escrow deposits and other assets	168,882	170,257
Total assets	6,872,405	7,003,982
LIABILITIES AND EQUITY
Secured debt	1,180,965	1,173,233
Unsecured notes	2,615,612	2,616,063
Unsecured lines of credit	20,293	20,293
Total long-term debt	3,816,870	3,809,589
Liabilities related to real estate investments held-for-sale	643	975
Construction payables and amounts due subcontractors, including retentions	51,309	55,775
Accrued real estate taxes	76,263	69,272
Accrued interest	33,675	58,904
Other accrued expenses	29,133	59,795
Other liabilities	132,734	131,735
Tenant security deposits and prepaid rents	46,383	38,355
Total liabilities	4,187,010	4,224,400
Partners’ equity:
Common equity (266,405 and 252,927 General Partner Units issued and outstanding)	2,028,588	1,923,886
Preferred equity (2,503 and 3,176 Preferred Units issued and outstanding)	625,638	793,910
General Partner's equity	2,654,226	2,717,796
Limited Partners' common equity (4,676 and 6,945 Limited Partner Units issued and outstanding)	25,027	56,254
Accumulated other comprehensive income	1,506	987
Total partners’ equity	2,680,759	2,775,037
Noncontrolling interests	4,636	4,545
Total equity	2,685,395	2,779,582
Liabilities and Equity	$ 6,872,405	$ 7,003,982