Investments in Real Estate and Real Estate Under Construction Summary of acquisitions and build-to-suit transactions (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013
Investments in Real Estate and Real Estate Under Construction [Line Items]
Initial Cost Basis	$ 166,468
Land	20,055
Building and Improvements	132,401
Lease in-place Value	14,012
Industrial Property [Member] | Long Island City New York [Member]
Investments in Real Estate and Real Estate Under Construction [Line Items]
Initial Cost Basis	42,124
Land	0
Building and Improvements	42,124
Lease in-place Value	0
Industrial Property [Member] | Houston, Texas [Member]
Investments in Real Estate and Real Estate Under Construction [Line Items]
Initial Cost Basis	81,400
Land	15,055
Building and Improvements	57,949
Lease in-place Value	8,396
Office Property [Member] | Denver Colorado [Member]
Investments in Real Estate and Real Estate Under Construction [Line Items]
Initial Cost Basis	34,547	[1]
Land	2,207	[1]
Building and Improvements	26,724	[1]
Lease in-place Value	5,616	[1]
Business Combination, Additional Consideration Transferred	3,825
Retail Property [Member] | Tuscaloosa Alabama [Member]
Investments in Real Estate and Real Estate Under Construction [Line Items]
Initial Cost Basis	8,397	[2]
Land	2,793	[2]
Building and Improvements	5,604	[2]
Lease in-place Value	0	[2]
Payments for Leasing Costs	$ 323

[1] The Company incurred additional initial costs of $3,825 which are included in “Other assets” in the accompanying unaudited condensed consolidated balance sheet.

[2] The Company incurred leasing costs of $323. The property was sold in September 2013.