ACQUISITIONS AND DISPOSITIONS (Acquisitions) (Details) $ in Thousands			1 Months Ended		3 Months Ended	12 Months Ended
	Sep. 04, 2015 USD ($)	Dec. 12, 2014 USD ($) ft² building	Oct. 31, 2014 USD ($) ft² item	Jul. 31, 2014 USD ($) ft²	Mar. 31, 2015 USD ($) ft²	Dec. 31, 2015 USD ($) ft²	Dec. 31, 2014 USD ($)	Mar. 31, 2014 ft²
Acquisitions
Gain on sale of The Club at Carlton Woods						$ 29,073
Seaport District Assemblage
Acquisitions
Area of real estate property acquired (in square foot) | ft²					58,000			42,694
South Street Seaport
Acquisitions
Area of real estate property acquired with total development rights | ft²					196,133			817,784
Purchase price					$ 91,400		$ 136,700
Conroe, Texas
Acquisitions
Area of real estate property acquired (in square foot) | ft²						2,055
Purchase price						$ 98,500
85 South Street
Acquisitions
Area of real estate property acquired (in square foot) | ft²			60,000
Purchase price			$ 20,100
Buildings acquired consolidated			8,100
Land acquired consolidated			$ 15,900
Number of story acquired | item			8
1701 Lake Robbins
Acquisitions
Area of real estate property acquired (in square foot) | ft²				12,376
Purchase price				$ 5,700
Buildings acquired consolidated				3,700
Land acquired consolidated				1,700
Intangible lease assets acquired consolidated				200
Assumption of Mortgage included in the purchase price				$ 4,600
110 N Wacker
Acquisitions
Fee interest percentage				100.00%
Fee interest purchased				$ 12,300
Leases, Acquired-in-Place | 1701 Lake Robbins
Acquisitions
Intangible lease assets acquired consolidated				300
Below Market Leases | 85 South Street
Acquisitions
Intangible lease assets acquired consolidated			$ (3,900)
Below Market Leases | 1701 Lake Robbins
Acquisitions
Intangible lease assets acquired consolidated				$ (100)
The Club at Carlton Woods | Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member]
Acquisitions
Proceeds from dispositions	$ 25,100
Liabilities assumed by purchaser	4,000
Gain on sale of The Club at Carlton Woods	29,100
Total assets	20,900
Total liabilities	$ 24,900
General Growth Properties
Acquisitions
Area of real estate property acquired with total development rights | ft²		699,884
Number of buildings | building		6
Purchase price		$ 130,000
Buildings acquired consolidated		79,200
Land acquired consolidated		23,400
Intangible lease assets acquired consolidated		27,400
General Growth Properties | Leases, Acquired-in-Place
Acquisitions
Intangible lease assets acquired consolidated		25,200
General Growth Properties | Above Market Leases
Acquisitions
Intangible lease assets acquired consolidated		3,800
General Growth Properties | Below Market Leases
Acquisitions
Intangible lease assets acquired consolidated		$ 1,600