Discontinued Operations (Details Textual) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013 property	Dec. 31, 2012 property	Dec. 31, 2011 property
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of impaired properties sold	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	3	1
Revenue related to properties sold	$ 7.0	$ 16.2	$ 22.1
Revenue related to properties held for sale	1.2	1.8	1.6
Expenses related to sale of real estate	2.1	7.4	12.0
Expense related to properties held for sale	1.5	1.2	0.7
Impairments related to sold property	0.4	11.1	1.7
Impairments related to property held for sale	6.2	3.8	5.0
Number of impaired properties sold	2	12	2
Number of impaired properties held for sale	3	1	5
Number of properties related to gain on sales	12	7	3
Land Parcel [Member] | Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairments related to sold property	$ 3.3