Commitments and Contingencies (Textual) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Commitments and Contingencies Disclosure [Abstract]
Outstanding commitments to fund real estate projects	$ 102,500,000
Outstanding Performance Bonds and Letters of Credit	2,400,000
Lease operating expenses	1,300,000	1,100,000	963,000
Future lease commitments	$ 146,700,000
Weighted average remaining terms of ground leases (in years)	86 years 7 months
Weighted average remaining terms of operating leases (in years)	1 year 8 months