Dispositions, Assets Held for Sale and Discontinued Operations (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues:
Rental income, disposed	$ 35,241	$ 115,759	$ 132,797
Expenses:
Interest expense, disposed	5,503	24,046	26,660
Property operating expenses, disposed	6,102	7,669	8,970
Depreciation expense, disposed	6,342	35,239	41,494
Expenses, disposed	17,947	66,954	77,124
Income (loss) from disposed properties	$ 17,294	$ 48,805	$ 55,673