Investments in Real Estate and Real Estate Under Construction Summary of properties to be acquired (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014
Business Acquisition [Line Items]
Estimated acquisition cost	$ 195,025
Auburn Hills, Michigan [Member] | Office Building [Member]
Business Acquisition [Line Items]
Estimated acquisition cost	40,025
Lease term (years)	14 years
Richland, Washington [Member] | Industrial property [Member]
Business Acquisition [Line Items]
Estimated acquisition cost	$ 155,000
Lease term (years)	20 years