Dispositions, Assets Held for Sale and Discontinued Operations (Details 2) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Revenues:
Rental income, disposed	$ 31,966	$ 36,626	$ 99,057	$ 113,950
Expenses:
Interest expense, disposed	4,939	7,282	16,697	23,594
Property operating expenses, disposed	1,476	1,695	4,411	4,944
Depreciation expense, disposed	4,604	9,119	20,873	31,568
Expenses, disposed	11,019	18,096	41,981	60,106
Income (loss) from disposed properties	$ 20,947	$ 18,530	$ 57,076	$ 53,844