Intangible Assets Intangible Assets (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Intangible Assets [Line Items]
Total Cost	$ 137,022	$ 152,611
Accumulated Amortization	(77,103)	(81,991)
Intangible Assets, net	59,919	70,620
In-place lease value
Intangible Assets [Line Items]
Total Cost	84,944	87,909
Accumulated Amortization	(43,027)	(42,894)
Intangible Assets, net	41,917	45,015
Tenant relationship value
Intangible Assets [Line Items]
Total Cost	48,939	56,137
Accumulated Amortization	(32,360)	(37,389)
Intangible Assets, net	16,579	18,748
Above market leases acquired
Intangible Assets [Line Items]
Total Cost	3,139	8,565
Accumulated Amortization	(1,716)	(1,708)
Intangible Assets, net	1,423	6,857
Below market leases acquired
Intangible Assets [Line Items]
Total Cost	77,004	77,083
Accumulated Amortization	(46,549)	(43,224)
Intangible Assets, net	$ 30,455	$ 33,859