Real Estate Investments - Discontinued Operations and Assets Held for Sale - Income Statement (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Revenues
Rental income	$ 101,472	$ 95,450	$ 200,212	$ 190,484
Expenses
Property operating	36,263	33,927	71,668	68,189
Bad debts, net of recoveries	78	27	39	(181)
Other Income (Expense)
Interest and other income, net	93	147	179	239
Discontinued Operations
Income from discontinued operations	(19)	330	(27)	663
Gain on sale of properties	7	0	7	0
INCOME (LOSS) FROM DISCONTINUED OPERATIONS	(12)	330	(20)	663
Discontinued Operations [Member]
Revenues
Rental income	0	348	0	690
Revenues	0	348	0	690
Expenses
Property operating	19	19	27	48
Bad debts, net of recoveries	0	(1)	0	(1)
Total Expenses	19	18	27	47
Other Income (Expense)
Interest and other income, net	0	0	0	20
Total other income (expense)	0	0	0	20
Discontinued Operations
Income from discontinued operations	(19)	330	(27)	663
Gain on sale of properties	7	0	7	0
INCOME (LOSS) FROM DISCONTINUED OPERATIONS	$ (12)	$ 330	$ (20)	$ 663