Disposition of Properties and Properties Held for Sale (Components of Assets Held for Sale) (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Long Lived Assets Held-for-sale [Line Items]
Rental property held for sale	$ 46,862	$ 46,005
Rental property, net [Member]
Long Lived Assets Held-for-sale [Line Items]
Rental property held for sale	44,252	43,532
Deferred lease costs and other intangibles, net [Member]
Long Lived Assets Held-for-sale [Line Items]
Rental property held for sale	888	757
Prepaids and other assets [Member]
Long Lived Assets Held-for-sale [Line Items]
Rental property held for sale	$ 1,722	$ 1,716