Commitments and Contingencies (Textual) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Commitments and Contingencies Disclosure [Abstract]
Outstanding commitments to fund real estate projects	$ 13,300,000
Outstanding Performance Bonds and Letters of Credit	2,600,000
Lease operating expenses	684,000	680,000	865,000
Future lease commitments	$ 16,019,000
Weighted average remaining terms of ground leases (in years)	69 years 8 months 12 days
Weighted average remaining terms of operating leases (in years)	3 years