INVESTMENT IN UNCONSOLIDATED JOINT VENTURES - Additional Information (Details)	1 Months Ended	3 Months Ended	12 Months Ended
	Apr. 30, 2012	Mar. 31, 2016 USD ($)	Dec. 31, 2017 USD ($) property		Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Aug. 07, 2015 USD ($)	Mar. 22, 2013	Apr. 15, 2011
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated joint ventures			$ 35,441,000	[1]	$ 34,025,000
Additional return on equity from Company's investments			0		1,017,000	$ 294,000
Management fees			18,341,000		21,365,000	15,205,000
Expenses from investment			15,291,000		15,861,000	15,849,000
Noncontrolling Interests in Consolidated Joint Ventures | Out-of-Period Adjustment Related to Prior Years
Schedule of Equity Method Investments [Line Items]
Additional return on equity from Company's investments		$ 900,000
24 Second Avenue Holdings LLC
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated joint ventures			30,533,000		30,306,000
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			1,100,000		1,400,000	600,000
Interest costs capitalized			1,300,000		900,000	300,000
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			36,500,000		21,600,000
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			36,500,000
Remaining borrowing capacity under credit agreement			0
Ladder Capital Realty Income Partnership I LP
Schedule of Equity Method Investments [Line Items]
Minimum average net equity partnership investment as a basis for management fee reduction			100,000,000
Management fees			0		6,905	$ 77,447
Ladder Capital Realty Income Partnership I LP | LP Units
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)									10.00%
Grace Lake JV, LLC
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated joint ventures			$ 4,908,000		$ 3,719,000
Percentage of equity kicker received with right to convert upon capital event	25.00%
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%
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			$ 30,000,000
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.