Real Estate Investments (Development Activities) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2016 USD ($) development_project	Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($)
Business Acquisition [Line Items]
Land and construction in progress	$ 15,900		$ 20,000
Number of development projects completed | development_project	35
Aggregate cost to date	$ 50,600
Number of remaining projects to be completed | development_project	2
Estimated completion period for remaining projects	3 months
Number of development projects placed into service | development_project	1
Aggregate cost of projects placed in service	$ 1,400
Interest Costs Capitalized	$ 100	$ 300
Number of other build-to-suit, redevelopment and expansion projects | development_project	4
Total commitment	$ 1,400
Land and Construction in Progress [Member]
Business Acquisition [Line Items]
Tenant Improvements	$ 3,200
2016 Acquisitions [Member]
Business Acquisition [Line Items]
Development projects in progress | development_project	6
Investment to date	$ 12,729
Estimated cost to complete	4,563
Total Investment	$ 17,292