Discontinued Operations (Details Textual) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) building property	Dec. 31, 2014 USD ($) property	Dec. 31, 2013 USD ($) property
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Properties Classified as Discontinued Operations | property	1
Number of impaired properties sold | building	1
Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties held for sale | property	1	2
Revenue related to properties sold	$ 0.8	$ 5.7	$ 14.0
Revenue related to properties held for sale			0.2
Expenses related to sale of real estate	0.1	4.7	8.7
Impairments related to property held for sale	$ 0.7	8.3	6.2
Impairments related to sold property		$ 3.7	$ 0.4
Number of impaired properties sold | property		3	2
Number of impaired properties held for sale | property		4	3
Number of properties related to gain on sales | property	1	3	12
Discontinued Operations [Member] | Land Parcel [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairments related to sold property			$ 3.3