INVESTMENT IN UNCONSOLIDATED JOINT VENTURES - Additional Information (Details)	1 Months Ended	3 Months Ended			9 Months Ended
	Apr. 30, 2012	Sep. 30, 2017 USD ($) Joint_Venture	Sep. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Sep. 30, 2017 USD ($) Joint_Venture	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)	Aug. 07, 2015 USD ($)	Mar. 22, 2013	Apr. 15, 2011
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated joint ventures		$ 35,007,000			$ 35,007,000		$ 34,025,000
Number of unconsolidated joint ventures | Joint_Venture		1			1
Additional return on equity from Company's investments					$ 0	$ 1,017,000
Management fees		$ 4,338,000	$ 8,101,000		13,378,000	17,258,000
Expenses from investment		3,709,000	4,030,000		11,193,000	11,943,000
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		30,393,000			30,393,000		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		300,000	400,000		800,000	1,100,000
Interest costs capitalized		400,000	200,000		900,000	600,000
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		32,300,000			32,300,000		21,600,000
24 Second Avenue Holdings LLC | Co-venturer | Construction Loan
Schedule of Equity Method Investments [Line Items]
Committed amount on credit agreement		50,500,000			50,500,000
Outstanding amount under credit agreement		32,300,000			32,300,000
Remaining borrowing capacity under credit agreement		0			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					100,000,000.0
Management fees			$ 0		0	$ 6,905
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		$ 4,614,000			$ 4,614,000		$ 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					75.00%
Grace Lake JV, LLC | LP Units
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)									25.00%
Grace Lake JV, LLC | Limited liability company
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)		25.00%			25.00%