Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Receivables, allowance	$ 1,403	$ 1,750
Accrued rental income, allowance	4,870	3,609
Debt costs, accumulated amortization	15,332	11,198
Notes payable - convertible, unamortized discount	6,363	12,201
Notes payable, unamortized discount	$ 5,033	$ 1,118
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	15,000,000	15,000,000
Series C, depositary shares issued		3,680,000
Series C, depositary shares outstanding	3,680,000	3,680,000
Series C, stated liquidation value per share	$ 25.00	$ 25.00
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	190,000,000	190,000,000
Common stock, shares issued	104,754,859	104,754,859
Common stock, shares issued and outstanding	83,613,289	83,613,289
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