Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Receivables, allowance	$ 1,113	$ 1,403
Accrued rental income, allowance	3,086	4,870
Debt costs, accumulated amortization	16,986	15,332
Debt Instrument, Unamortized Premium	216	0
Notes payable - convertible, unamortized discount	4,256	6,363
Notes payable, unamortized discount	$ 4,763	$ 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	107,449,071	104,754,859
Common stock, shares issued and outstanding	107,449,071	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 D and Series C, depositary shares issued	11,500,000	0
Series D and Series C, depositary shares outstanding	11,500,000	0
Series D and Series C, stated liquidation value per share	$ (25)	$ 0
Series C Depositary Share [Member]
Series D and Series C, depositary shares issued	0	3,680,000
Series D and Series C, depositary shares outstanding	0	3,680,000
Series D and Series C, stated liquidation value per share	$ 0	$ (25)