INVESTMENT IN UNCONSOLIDATED JOINT VENTURES - Additional Information (Details)	1 Months Ended	3 Months Ended
	Apr. 30, 2012	Mar. 31, 2018 USD ($) property		Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)	Aug. 07, 2015 USD ($)	Mar. 22, 2013
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated joint ventures		$ 34,564,000	[1]		$ 35,441,000
Proceeds from distribution of investment		1,250,000		$ 0
Expenses from investment		3,572,000		5,798,000
Committed amount on credit agreement		450,000,000
Grace Lake JV, LLC
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated joint ventures		3,925,000			4,908,000
Percentage of equity kicker received with right to convert upon capital event	25.00%
Proceeds from distribution of investment		$ 1,300,000
Preferred return used to determine distribution of excess cash flow (as a percent)		8.25%
Percentage of distribution of all excess cash flows and all disposition proceeds upon any sale entitled after consideration of preferred return and return of equity remaining in the property to operating partner		25.00%
Percentage of investment of operating partner		81.00%
Grace Lake JV, LLC | LP Units
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)							19.00%
Grace Lake JV, LLC | Limited liability company
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)		19.00%
24 Second Avenue Holdings LLC
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated joint ventures		$ 30,639,000			30,533,000
Ownership interest (as a percent)						73.80%
Amount contributed						$ 31,100,000
Profit multiplier ratio						1.70
Ownership percentage after achievement of profit multiplier ratio						50.00%
Expenses from investment		200,000		300,000
Interest costs capitalized		300,000		$ 200,000
24 Second Avenue Holdings LLC | Operating Partner
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)						26.20%
Ownership percentage after achievement of profit multiplier ratio						50.00%
24 Second Avenue Holdings LLC | Co-venturer
Schedule of Equity Method Investments [Line Items]
Loans payable outstanding from unconsolidated joint venture		39,000,000			$ 36,500,000
24 Second Avenue Holdings LLC | Co-venturer | Construction Loan
Schedule of Equity Method Investments [Line Items]
Committed amount on credit agreement		50,465,000
Outstanding amount under credit agreement		39,000,000
Remaining borrowing capacity under credit agreement		$ 0
Apartment Building | 24 Second Avenue Holdings LLC
Schedule of Equity Method Investments [Line Items]
Number of real estate properties | property		31
Number of real estate properties, under contract | property		11
Real estate properties, under contract		$ 30,400,000
Real estate properties, under contract, deposit		10.00%
Other | 24 Second Avenue Holdings LLC
Schedule of Equity Method Investments [Line Items]
Number of real estate properties | property		1

[1] Includes amounts relating to consolidated variable interest entities. See Note 3.