CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Per Share data	Sep. 30, 2011	Dec. 31, 2010
CONSOLIDATED BALANCE SHEETS
Properties held-for-sale, accumulated depreciation and amortization (in dollars)	$ 613	$ 505
Mortgage loans receivable, allowance for doubtful accounts (in dollars)	931	981
Straight-line rent receivable, allowance for doubtful accounts (in dollars)	668	634
Other assets related to properties held-for-sale, allowance for doubtful accounts (in dollars)	839	839
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	15,000	15,000
Preferred stock, shares issued	2,000	5,536
Preferred stock, shares outstanding	2,000	5,536
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	45,000	45,000
Common stock, shares issued	30,341	26,345
Common stock, shares outstanding	30,341	26,345
Straight-line rent receivable from a lessee that qualifies as a related party (in dollars)	3,002	2,822
Marketable securities issued by an entity that qualifies as a related party (in dollars)	$ 6,500	$ 6,500