Subsequent Events (Details) $ in Thousands, ft² in Millions	1 Months Ended	6 Months Ended
	Jul. 22, 2016 USD ($) ft² a bldg	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)
Subsequent Event [Line Items]
Proceeds from Sale of Real Estate Held-for-investment		$ 139,814	$ 156,891
2016 sales [Member] | Disposal Group, Not Discontinued Operations [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Number of Real Estate Properties | bldg	108
Area of Real Estate Property | ft²	7.6
Area of Land | a	26.7
Proceeds from Sale of Real Estate Held-for-investment	$ 969,000