Dispositions, Assets Held for Sale and Discontinued Operations (Details 2) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenues:
Rental income, disposed	$ 13,886	$ 43,787
Expenses:
Interest expense, disposed	127	2,707
Property operating expenses, disposed	7,256	8,521
Provision for depreciation, disposed	1,741	9,813
Expenses, disposed	9,124	21,041
Income (loss) from disposed properties	$ 4,762	$ 22,746