CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
CONSOLIDATED BALANCE SHEETS
Properties held-for-sale, accumulated depreciation and amortization (in dollars)	$ 0	$ 1,650
Mortgage loans receivable, allowance for doubtful accounts (in dollars)	782	921
Straight-line rent receivable, allowance for doubtful accounts (in dollars)	1,557	1,519
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	2,000
Preferred stock, shares outstanding	2,000	2,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	60,000	45,000
Common stock, shares issued	30,544	30,346
Common stock, shares outstanding	30,544	30,346
Straight-line rent receivable from a lessee that qualifies as a related party (in dollars)	3,191	3,060
Marketable securities issued by an entity that qualifies as a related party (in dollars)		$ 6,500
Number of authorized shares of common stock before amendment	45,000