Condensed Consolidated Balance Sheets (USD $)	Sep. 30, 2012	Dec. 31, 2011
Assets
Land	$ 62,693,000	$ 49,114,000
Buildings and improvements	625,361,000	487,396,000
Construction in progress	718,000	4,983,000
Real estate properties, gross	688,772,000	541,493,000
Less accumulated depreciation	(169,293,000)	(146,698,000)
Real estate properties, net	519,479,000	394,795,000
Mortgage notes receivable, net	79,325,000	78,672,000
Investment in preferred stock, at cost	38,132,000	38,132,000
Cash and cash equivalents	4,410,000	15,886,000
Marketable securities	11,806,000	11,364,000
Accounts Receivable, Net	593,000	1,236,000
Straight-line rent receivable	11,030,000	8,706,000
Deferred costs and other assets	11,091,000	2,627,000
Assets held for sale, net	0	29,381,000
Total Assets	675,273,000	579,563,000
Liabilities and Stockholders' Equity
Long-term Line of Credit	194,250,000	97,300,000
Real estate purchase liabilities	6,478,000	9,478,000
Accounts payable and accrued expenses	4,114,000	3,483,000
Dividends Payable	18,646,000	24,144,000
Deferred income	1,374,000	1,673,000
Total Liabilities	224,862,000	136,078,000
Commitments and Contingencies
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract]
Common stock, $.01 par value; 40,000,000 shares authorized; 27,709,611 and 27,689,392 shares issued and outstanding, respectively	278,000	278,000
Capital in excess of par value	467,600,000	465,678,000
Cumulative dividends in excess of net income	(34,806,000)	(29,652,000)
Accumulated Other Comprehensive Income (Loss), Net of Tax	6,375,000	7,181,000
Total Stockholders' Equity	439,447,000	443,485,000
Total Equity	450,411,000	443,485,000
Total Liabilities and Stockholders' Equity	675,273,000	579,563,000
Noncontrolling Interest [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract]
Noncontrolling interest	10,964,000	0
Total Equity	$ 10,964,000