Real Estate Investments - Discontinued Operations and Assets Held for Sale - Income Statement (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Revenues
Rental income	$ 106,561	$ 102,534	$ 315,519	$ 302,746
Expenses
Property operating	40,626	37,504	116,644	109,173
Bad debts, net of recoveries	14	(47)	185	(8)
Other Income (Expense)
Interest and other income, net	426	123	616	301
Discontinued Operations
Income (Loss) from discontinued operations	8	(23)	(9)	(50)
Gain on sale of properties	0	0	5	7
INCOME (LOSS) FROM DISCONTINUED OPERATIONS	8	(23)	(4)	(43)
Discontinued Operations
Revenues
Rental income	0	0	0	0
Revenues	0	0	0	0
Expenses
Property operating	2	23	19	50
Bad debts, net of recoveries	(10)	0	(10)	0
Total Expenses	(8)	23	9	50
Other Income (Expense)
Interest and other income, net	0	0	0	0
Total other income (expense)	0	0	0	0
Discontinued Operations
Income (Loss) from discontinued operations	8	(23)	(9)	(50)
Gain on sale of properties	0	0	5	7
INCOME (LOSS) FROM DISCONTINUED OPERATIONS	$ 8	$ (23)	$ (4)	$ (43)