Schedule III - Real Estate and Accumulated Depreciation (Summary Schedule) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Real Estate and Accumulated Depreciation Disclosure [Abstract]
Real Estate, Gross	$ 698,536	$ 541,493	$ 463,197	$ 350,786
Payments to Acquire Property, Plant, and Equipment	110,601	75,806	98,736
Additions Through Contingent Liabilities	0	5,478	1,000
Noncash or Part Noncash Acquisition, Debt Assumed	19,250	0	0
Additions Through Assumption Of Debt	10,964	0	0
Additions Through Settlement Of Mortgage Note	0	0	22,936
Real Estate, Cost of Real Estate Sold	(17,259)	(2,988)	(5,000)
Real Estate, Other Additions	39,323	0	0
Real Estate, Other Deductions	(5,836)	0	(5,261)
Real Estate Accumulated Depreciation	163,146	146,698	135,543	126,925
Real Estate Accumulated Depreciation, Depreciation Expense	16,981	11,992	11,203
Real Estate Accumulated Depreciation, Real Estate Sold	(6,250)	(837)	(769)
Real Estate Accumulated Depreciation, Other Additions	9,942	0	0
Real Estate Accumulated Depreciation, Other Deductions	$ (4,225)	$ 0	$ (1,816)