Dispositions, Assets Held for Sale and Discontinued Operations (Details 2) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Revenues:
Rental income, disposed	$ 7,463,000	$ 30,857,000	$ 15,944,000	$ 62,817,000
Expenses:
Interest expense, disposed	1,463,000	6,020,000	2,744,000	13,875,000
Property operating expenses, disposed	1,482,000	2,257,000	3,009,000	4,422,000
Depreciation expense, disposed	2,394,000	9,316,000	4,277,000	19,059,000
Expenses, disposed	5,339,000	17,593,000	10,030,000	37,356,000
Income (loss) from disposed properties	$ 2,124,000	$ 13,264,000	$ 5,914,000	$ 25,461,000