Real Estate Investments (Development Activities) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) development_project	Dec. 31, 2014 USD ($)
Business Acquisition [Line Items]
Number of development projects completed | development_project	31
Aggregate cost to date	$ 45,100
Number of remaining projects to be completed | development_project	6
Estimated completion period for remaining projects	12 months
Number of development projects placed into service | development_project	2
Aggregate cost of projects placed in service	$ 55,000
Interest Costs Capitalized	$ 1,200	$ 300
Number of other build-to-suit, redevelopment and expansion projects | development_project	4
Investment to date	$ 20,014	$ 77,450
Total commitment	1,900
Land and Construction in Progress [Member]
Business Acquisition [Line Items]
Tenant Improvements	$ 2,800
2015 Acquisitions [Member]
Business Acquisition [Line Items]
Development projects in progress | development_project	10
Investment to date	$ 17,185
Estimated cost to complete	3,660
Total Investment	$ 20,845