Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Accounts receivable, allowance	$ 2,693	$ 3,597
Straight-line rent receivable, allowance	6,997	7,447
Deferred financing costs, accumulated amortization	42,720	59,109
Deferred leasing and other costs, accumulated amortization	$ 311,525	$ 292,334
Preferred shares, par value	$ 0.01	$ 0.01
Preferred shares, shares authorized	5,000	5,000
Preferred shares, shares issued	2,503	3,176
Preferred shares, shares outstanding	2,503	3,176
Common shares, par value	$ 0.01	$ 0.01
Common shares, shares authorized	400,000	400,000
Common shares, shares issued	266,405	252,927
Common shares, shares outstanding	266,405	252,927