Intangible Assets Intangible Assets (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Intangible Assets [Line Items]
Total Cost	$ 130,275	$ 152,611
Accumulated Amortization	(75,818)	(81,991)
Intangible Assets, net	54,457	70,620
In-place lease value
Intangible Assets [Line Items]
Total Cost	81,410	87,909
Accumulated Amortization	(42,629)	(42,894)
Intangible Assets, net	38,781	45,015
Tenant relationship value
Intangible Assets [Line Items]
Total Cost	46,160	56,137
Accumulated Amortization	(31,786)	(37,389)
Intangible Assets, net	14,374	18,748
Above market leases acquired
Intangible Assets [Line Items]
Total Cost	2,705	8,565
Accumulated Amortization	(1,403)	(1,708)
Intangible Assets, net	1,302	6,857
Below Market Leases Acquired [Member]
Intangible Assets [Line Items]
Total Cost	76,874	77,083
Accumulated Amortization	(48,374)	(43,224)
Intangible Assets, net	$ 28,500	$ 33,859