Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Receivables, allowance	$ 1,843	$ 1,403
Accrued rental income, allowance	4,875	4,870
Debt costs, accumulated amortization	16,159	15,332
Notes payable - convertible, unamortized discount	5,319	6,363
Notes payable, unamortized discount	$ 4,897	$ 5,033
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	15,000,000	15,000,000
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	190,000,000	190,000,000
Common stock, shares issued	106,595,333	104,754,859
Common stock, shares issued and outstanding	106,595,333	104,754,859
Excess stock, par value	$ 0.01	$ 0.01
Excess stock, shares authorized	205,000,000	205,000,000
Excess stock, shares issued	0	0
Excess stock, shares outstanding	0	0
Series D Depositary Share [Member]
Series C, depositary shares issued	11,500,000	0
Series C, depositary shares outstanding	11,500,000	0
Series C, stated liquidation value per share	$ 25.00	$ 0.00
Series C Depositary Share [Member]
Series C, depositary shares issued	0	3,680,000
Series C, depositary shares outstanding	0	3,680,000
Series C, stated liquidation value per share	$ 0.00	$ 25.00