Real Estate Investments - Discontinued Operations and Assets Held for Sale - Income Statement (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Revenues
Rental income	$ 102,534	$ 95,383	$ 302,746	$ 285,867
Expenses
Property operating	37,504	35,247	109,173	103,437
Bad debts, net of recoveries	(47)	(21)	(8)	(202)
Other Income (Expense)
Interest and other income, net	123	72	301	311
Discontinued Operations
Income (Loss) from discontinued operations	(23)	61	(50)	725
Gain on sale of properties	0	10,571	7	10,571
INCOME (LOSS) FROM DISCONTINUED OPERATIONS	(23)	10,632	(43)	11,296
Discontinued Operations [Member]
Revenues
Rental income	0	62	0	752
Revenues	0	62	0	752
Expenses
Property operating	23	2	50	48
Bad debts, net of recoveries	0	(1)	0	(1)
Total Expenses	23	1	50	47
Other Income (Expense)
Interest and other income, net	0	0	0	20
Total other income (expense)	0	0	0	20
Discontinued Operations
Income (Loss) from discontinued operations	(23)	61	(50)	725
Gain on sale of properties	0	10,571	7	10,571
INCOME (LOSS) FROM DISCONTINUED OPERATIONS	$ (23)	$ 10,632	$ (43)	$ 11,296