Schedule III - Real Estate and Accumulated Depreciation (Summary Schedule) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Investment in Real Estate:
Balance at beginning of period, Investment in Real Estate	$ 463,197	$ 350,786	$ 310,906
Additions through cash expenditures	75,806	98,736	81,569
Additions through contingent liabilities	5,478	1,000	3,000
Additions through settlement of mortgage note		22,936
Sale of properties for cash	(2,988)	(5,000)
Reclassification for assets held for sale		(5,261)	(44,689)
Balance at end of year, Investment in Real Estate	541,493	463,197	350,786
Accumulated Depreciation:
Balance at beginning of period, Accumulated Depreciation	135,543	126,925	129,574
Addition charged to costs and expenses	11,992	11,203	8,620
Sale of properties	(837)	(769)
Reclassification for assets held for sale		(1,816)	(11,269)
Balance at end of year, Accumulated Depreciation	$ 146,698	$ 135,543	$ 126,925