Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Accounts receivable, allowance	$ 2,753	$ 3,597
Straight-line rent receivable, allowance	6,565	7,447
Deferred financing costs, accumulated amortization	45,667	59,109
Deferred leasing and other costs, accumulated amortization	337,543	292,334
Preferred shares, par value	$ 0.01	$ 0.01
Preferred shares, shares authorized	5,000,000	5,000,000
Preferred shares, shares issued	2,503,000	3,176,000
Preferred shares, shares outstanding	2,503,000	3,176,000
Common shares, par value	$ 0.01	$ 0.01
Common shares, shares authorized	400,000,000	400,000,000
Common shares, shares issued	267,523,000	252,927,000
Common shares, shares outstanding	267,523,000	252,927,000
Subsidiary of Common Parent [Member]
Accounts receivable, allowance	2,753	3,597
Straight-line rent receivable, allowance	6,565	7,447
Deferred financing costs, accumulated amortization	45,667	59,109
Deferred leasing and other costs, accumulated amortization	$ 337,543	$ 292,334
Common equity, General Partner Units issued	267,523,000	252,927,000
Common equity, General Partner Units outstanding	267,523,000	252,927,000
Preferred Units, Issued	2,503,000	3,176,000
Preferred Units, Outstanding	2,503,000	3,176,000
Limited Partner Units issued	4,511,000	6,945,000
Limited Partner Units outstanding	4,511,000	6,945,000