SUBSEQUENT EVENTS (Details) $ in Thousands	1 Months Ended				3 Months Ended	12 Months Ended
	Feb. 28, 2017 USD ($) loan	Jan. 31, 2017 USD ($) office_building loan store	Sep. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Subsequent Event [Line Items]
Sales price, gross						$ 194,710	$ 104,860	$ 18,615
Loss on impairment						116,822	105,945	$ 17,858
Mortgage and other indebtedness, variable-rate debt						888,770	1,241,379
Mortgage and other notes receivable						16,803	18,238
Non Recourse Loans On Operating Properties
Subsequent Event [Line Items]
Mortgage and other indebtedness, variable-rate debt						19,055	16,840
Subsequent Event
Subsequent Event [Line Items]
Purchase price		$ 7,000
One and Two Oyster Point
Subsequent Event [Line Items]
Loss on impairment			$ 3,844
One and Two Oyster Point | Subsequent Event
Subsequent Event [Line Items]
Number of office buildings sold | office_building		2
Sales price, gross		$ 6,250
Loss on impairment		$ 3,844
Midland Mall, Midland, MI
Subsequent Event [Line Items]
Loss on impairment				$ 4,681
Midland Mall, Midland, MI | Non Recourse Loans On Operating Properties
Subsequent Event [Line Items]
Mortgage and other indebtedness, variable-rate debt						31,953
Midland Mall, Midland, MI | Subsequent Event | Non Recourse Loans On Operating Properties
Subsequent Event [Line Items]
Gain on extinguishment of debt					$ 4,088
The Plaza at Lafayette and The Shoppes at St. Clair | Mortgages
Subsequent Event [Line Items]
Mortgage and other indebtedness, variable-rate debt						55,973
The Plaza at Lafayette and The Shoppes at St. Clair | Subsequent Event | Mortgages
Subsequent Event [Line Items]
Number of loans retired | loan		2
Hamilton Corner, Chattanooga, TN | Subsequent Event | Mortgages
Subsequent Event [Line Items]
Mortgage and other indebtedness, variable-rate debt	$ 104,179
Number of loans retired | loan	2
Sears Department Stores | Subsequent Event
Subsequent Event [Line Items]
Number of business acquired | store		5
Sears Auto Centers | Subsequent Event
Subsequent Event [Line Items]
Number of business acquired | store		2
Sears Department Stores and Auto Centers | Subsequent Event
Subsequent Event [Line Items]
Purchase price		$ 72,500
Lease term (in years)		10 years
Monthly lease revenue receivable		$ 5,075
Required notice period for cancellation of lease (in months)		6 months
Macy's | Subsequent Event
Subsequent Event [Line Items]
Number of business acquired | store		4
Notes Receivable
Subsequent Event [Line Items]
Mortgage and other notes receivable						11,123	10,462
Horizon Group | Notes Receivable
Subsequent Event [Line Items]
Mortgage and other notes receivable						$ 300	$ 0
Horizon Group | Notes Receivable | Subsequent Event
Subsequent Event [Line Items]
Mortgage and other notes receivable		$ 300