Real Estate - Held for Sale (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012 properties	Dec. 31, 2011 properties	Dec. 31, 2010 properties
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number Of Properties Classified As Held For Sale	23	22
Number Of Improved Properties Held for Sale	16	16
Number of Land Parcels Held for Sale	7	6
Land and improvements	$ 15,751	$ 14,172
Building and improvements	37,080	32,044
Real Estate Held-for-sale	52,831	46,216
Less impairment	(10,518)	(8,774)
Inventory, Real Estate, Held-for-sale	41,773	36,936
Number Of Disposed Properties Continuing Operations	0	0	2
Number Of Disposed Properties Discontinued Operations	34	8	16
Number of Disposed Properties Noncontrolling Interests	0	0	0
Number Of Disposed Properties Continuing and Discontinued Operations	34	8	18
Gain on disposition of real estate	0	297	641
Gain (Loss) on Disposition of Assets, Noncontrolling Interest Portion, Discontinued Operations	0	(194)	(363)
Gain (Loss) on Disposition of Assets, Total, Continuing and Discontinued Operations	10,956	527	1,712
Assets Held-for-sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Less accumulated depreciation and amortization	(540)	(506)
Gain on disposition of real estate	$ 10,956	$ 424	$ 1,434