ORGANIZATION AND BASIS OF PRESENTATION (Details)		3 Months Ended			9 Months Ended		12 Months Ended
	Aug. 10, 2016 USD ($) Institutional_Investor	Sep. 30, 2016 USD ($) property	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) property	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Number of retail properties (in properties) | property		175			175
Reallocation of noncontrolling interest		$ 35,300,000			$ 0		$ 31,800,000
Impairment of asset		$ 0	$ 0		$ 0	$ 5,000,000
Brandywine Portfolio
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Noncontrolling interest, ownership percentage				77.78%
Impairment of asset				$ 5,000,000
Core Portfolio
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Number of retail properties (in properties) | property		116			116
Impairment of asset						5,000,000
Opportunity Funds
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Number of retail properties (in properties) | property		59			59
Impairment of asset						$ 0
Operating Partnership | Fund V
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Ownership interest by general partner or managing partner					20.10%
Equity commitment, amount	$ 520,100,000.0	$ 520,100,000			$ 520,100,000
Number of institutional investors | Institutional_Investor	12
Closed equity commitments	$ 104,500,000.0
Preferred Return					6.00%
Capital Called	$ 0				$ 0
Operating Partnership | Brandywine Portfolio
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Impairment of asset				$ 1,100,000
Mortgages
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Debt instrument face amount		129,044,000			129,044,000
Non-Recourse Mortgage Debt Due 2016 | Mortgages
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Debt instrument face amount		$ 26,300,000.0			$ 26,300,000.0
Operating Partnership, as General Partner or Managing Member
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Ownership interest by general partner or managing partner					95.00%
Remaining funds rate of distribution to partnership		20.00%			20.00%
Institutional Investors
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Remaining funds rate of distribution to all partners		80.00%			80.00%