Segment Reporting (Details Textual) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013 Properties Business_Segments		Mar. 31, 2012
Segment Reporting (Textual) [Abstract]
Number of Operating Segments	5
Number of properties generated by rental revenue	400
Provision for asset impairment	$ 13,932	[1]	$ 3,540	[2]
SunTrust Banks, Inc. [Member]
Segment Reporting (Textual) [Abstract]
Percentage of rental revenue	10.00%
AT&T, Inc. [Member]
Segment Reporting (Textual) [Abstract]
Percentage of rental revenue	9.00%
Number of Leased Properties	3
Retail [Member]
Segment Reporting (Textual) [Abstract]
Provision for asset impairment	(12,816)	[1]
Industrial [Member]
Segment Reporting (Textual) [Abstract]
Provision for asset impairment	$ (1,116)	[1]

[1] rovision for asset impairment, $12,816 related to retail properties and $1,116 related to an industrial property.

[2] .