Operating Property (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011 property	Dec. 31, 2010
Operating Property [Abstract]
Depreciation	$ 14,900,000	$ 14,900,000	$ 13,000,000
Property impairment		$ 65,000
Number of impaired properties		2