Real Estate Investments - Discontinued Operations and Assets Held for Sale - Income Statement (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenues
Rental income	$ 104,869	$ 101,472	$ 208,957	$ 200,212
Expenses
Property operating	38,184	36,263	76,018	71,668
Other Income (Expense)
Interest and other income, net	77	93	189	179
Discontinued Operations
Loss from discontinued operations	0	(19)	(17)	(27)
Gain on sale of properties	0	7	5	7
LOSS FROM DISCONTINUED OPERATIONS	0	(12)	(12)	(20)
Discontinued Operations
Revenues
Rental income	0	0	0	0
Revenues	0	0	0	0
Expenses
Property operating	0	19	17	27
Total Expenses	0	19	17	27
Other Income (Expense)
Interest and other income, net	0	0	0	0
Total other income (expense)	0	0	0	0
Discontinued Operations
Loss from discontinued operations	0	(19)	(17)	(27)
Gain on sale of properties	0	7	5	7
LOSS FROM DISCONTINUED OPERATIONS	$ 0	$ (12)	$ (12)	$ (20)