Intangible Assets (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Intangible assets
Total Cost	$ 196,147	$ 152,611
Accumulated Amortization	(63,818)	(81,991)
Intangible Assets, net	132,329	70,620
In-place lease value [Member]
Intangible assets
Total Cost	150,782	87,909
Accumulated Amortization	(35,607)	(42,894)
Intangible Assets, net	115,175	45,015
Tenant relationship value [Member]
Intangible assets
Total Cost	38,692	56,137
Accumulated Amortization	(26,868)	(37,389)
Intangible Assets, net	11,824	18,748
Above market leases acquired [Member]
Intangible assets
Total Cost	6,673	8,565
Accumulated Amortization	(1,343)	(1,708)
Intangible Assets, net	5,330	6,857
Below market leases acquired [Member]
Intangible assets
Total Cost	81,991	77,083
Accumulated Amortization	(47,547)	(43,224)
Intangible Assets, net	$ 34,444	$ 33,859