Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Accounts receivable, allowance	$ 3,616	$ 3,374
Straight-line rent receivable, allowance	6,107	6,091
Deferred financing costs, accumulated amortization	50,582	48,218
Deferred leasing and other costs, accumulated amortization	381,325	372,047
Preferred shares, par value	$ 0.01	$ 0.01
Preferred shares, shares authorized	5,000,000	5,000,000
Preferred shares, shares issued	1,791,000	2,503,000
Preferred shares, shares outstanding	1,791,000	2,503,000
Common shares, par value	$ 0.01	$ 0.01
Common shares, shares authorized	400,000,000	400,000,000
Common shares, shares issued	321,667,000	279,423,000
Common shares, shares outstanding	321,667,000	279,423,000
Subsidiary of Common Parent [Member]
Accounts receivable, allowance	3,616	3,374
Straight-line rent receivable, allowance	6,107	6,091
Deferred financing costs, accumulated amortization	50,582	48,218
Deferred leasing and other costs, accumulated amortization	$ 381,325	$ 372,047
Common equity, General Partner Units issued	321,667,000	279,423,000
Common equity, General Partner Units outstanding	321,667,000	279,423,000
Preferred Units, Issued	1,791,000	2,503,000
Preferred Units, Outstanding	1,791,000	2,503,000
Limited Partner Units issued	4,388,000	4,419,000
Limited Partner Units outstanding	4,388,000	4,419,000