Investments in Real Estate and Real Estate Under Construction - Summary of properties to be acquired (Details) - 6 months ended Jun. 30, 2015 - USD ($) $ in Thousands	Total
Business Acquisition [Line Items]
Estimated acquisition cost	$ 184,680
Richland, Washington [Member] | Industrial property [Member]
Business Acquisition [Line Items]
Estimated acquisition cost	$ 155,000
Lease term (years)	20 years
Detroit, Michigan [Member] | Industrial property [Member]
Business Acquisition [Line Items]
Estimated acquisition cost	$ 29,680
Lease term (years)	20 years