Dispositions, Assets Held for Sale and Discontinued Operations (Details 2) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenues:
Rental income, disposed	$ 4,094	$ 19,990	$ 21,494	$ 38,552
Expenses:
Interest expense, disposed	284	2,506	1,714	5,032
Property operating expenses, disposed	2,020	1,338	5,098	2,700
Depreciation expense, disposed	475	3,071	1,121	7,022
Expenses, disposed	2,779	6,915	7,933	14,754
Income (loss) from disposed properties	$ 1,315	$ 13,075	$ 13,561	$ 23,798