Property Transactions (Fair Value of Assets and Liabilities Acquired) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Business acquisition cost of acquired entity purchase price allocation
Land and improvements	$ 5,987	$ 13,439
Building	36,705	94,190
Tenant Improvements and FF&E	9,034	8,600
Tangible assets	51,726	116,229
Intangible Assets:
Above-market leases	3,267	3,991
In-place leases	8,888	16,172
Total intangible assets	12,155	20,163
Intangible Liabilities:
Below-market leases	(436)	(1,659)
Total net assets acquired	$ 63,445	$ 134,733