Dispositions, Assets Held for Sale and Discontinued Operations (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues:
Rental income, disposed	$ 310,390	$ 352,615	$ 401,640
Expenses:
Interest expense, disposed	49,599	64,741	80,893
Property operating expenses, disposed	10,846	12,117	14,127
Depreciation expense, disposed	68,280	88,580	111,593
Expenses, disposed	128,725	165,438	206,613
Income (loss) from disposed properties	$ 181,665	$ 187,177	$ 195,027