DEBT OBLIGATIONS (Details)								3 Months Ended		9 Months Ended		12 Months Ended
	Aug. 03, 2016 USD ($) Extension	Apr. 19, 2016 Extension	Mar. 21, 2016 USD ($)	Oct. 25, 2015 USD ($) Extension	Oct. 31, 2014 USD ($)	Feb. 11, 2014 USD ($) Extension	Jan. 24, 2013 USD ($) Financing_Counterparty	Sep. 30, 2016 USD ($) servicing_asset counterparty Extension	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) agreement counterparty Extension	Sep. 30, 2015 USD ($) agreement	Dec. 31, 2015 USD ($) Extension	Jul. 01, 2016 USD ($)	Jun. 28, 2016 USD ($)	Feb. 19, 2016	Aug. 14, 2015 USD ($) Extension	Apr. 10, 2015 USD ($) Extension	Feb. 19, 2015 Extension
Committed Loan and Securities Repurchase Facilities
Debt obligations outstanding								$ 1,458,327,000		$ 1,458,327,000		$ 1,260,755,000
Borrowing Under Credit Facilties and Debt Issuance Costs [Abstract]
Restricted equity from payment as dividend								$ 899,400,000		899,400,000
Mortgage Loans on Real Estate [Abstract]
Amortization of premiums										$ (660,000)	$ (678,000)
Number of assets transferred accounted for as secured borrowings | servicing_asset								3
Borrowings from Federal Home Loan Bank (FHLB) [Abstract]
Percent of FHLB advances to total debt obligations outstanding								40.10%		40.10%
Tuebor
Borrowings from Federal Home Loan Bank (FHLB) [Abstract]
Amount restricted from transfer								$ 591,500,000		$ 591,500,000
Mortgage loan receivables held for investment
Mortgage Loans on Real Estate [Abstract]
Transfer of financial assets (loans) treated as sales								324,400,000		324,400,000
Revolving credit facility | One-Month LIBOR
Committed Loan and Securities Repurchase Facilities
Number of extension maturity periods | Extension						2
Length of extension options						12 months
Borrowing Under Credit Facilties and Debt Issuance Costs [Abstract]
Basis spread on variable rate (as a percent)						3.50%
Committed amount on credit agreement						$ 143,000,000
Debt borrowings term						3 years
Letters of credit
Borrowing Under Credit Facilties and Debt Issuance Costs [Abstract]
Committed amount on credit agreement						$ 25,000,000
Term master repurchase agreement
Committed Loan and Securities Repurchase Facilities
Committed amount on master repurchase agreement								400,000,000		$ 400,000,000
Number of extension maturity periods | Extension																		1
Committed Loan repurchase facility
Committed Loan and Securities Repurchase Facilities
Number of agreements | agreement										5
Committed amount on master repurchase agreement								1,650,000,000		$ 1,650,000,000		1,485,000,000
Debt obligations outstanding								622,643,000		622,643,000		704,149,000
Total Repurchase Facilities
Committed Loan and Securities Repurchase Facilities
Committed amount on master repurchase agreement								2,050,000,000		2,050,000,000		1,785,000,000
Debt obligations outstanding								$ 1,458,327,000		$ 1,458,327,000		1,260,755,000
Total Repurchase Facilities | Deutshe Bank, J.P. Morgan and Wells Fargo
Committed Loan and Securities Repurchase Facilities
Repurchase agreements, number of counterparties | counterparty								9		9
Excess collateral over amounts borrowed under repurchase agreements								$ 75,000,000		$ 75,000,000
Ratio indebtedness over total equity (as a percent)										5.00%
Haircut on repurchase agreements (as a percent)								29.70%		29.70%
Uncommitted securities Repurchase Facilities | Minimum
Borrowing Under Credit Facilties and Debt Issuance Costs [Abstract]
Advance rates (as a percent)										65.00%
Uncommitted securities Repurchase Facilities | Maximum
Borrowing Under Credit Facilties and Debt Issuance Costs [Abstract]
Advance rates (as a percent)										95.00%
Mortgage loan financing
Mortgage Loans on Real Estate [Abstract]
Transfers of assets accounted for as secured borrowings, carrying amount								$ 137,600,000		$ 137,600,000
Transfers of assets accounted for as secured borrowings, non-nontrolling pari passu interests								61,600,000		61,600,000
Proceeds from transfers of assets accounted for as sales								63,200,000
1/2016 | Uncommitted securities Repurchase Facilities
Committed Loan and Securities Repurchase Facilities
Debt obligations outstanding												394,719,000
5/24/2016 | Committed Loan repurchase facility
Committed Loan and Securities Repurchase Facilities
Committed amount on master repurchase agreement												$ 450,000,000
Number of extension maturity periods | Extension												2
Length of extension options												12 months
Debt obligations outstanding												$ 269,779,000
4/10/2019 | Term master repurchase agreement
Committed Loan and Securities Repurchase Facilities
Number of extension maturity periods | Extension																	1
4/9/2017 | Committed Loan repurchase facility
Committed Loan and Securities Repurchase Facilities
Committed amount on master repurchase agreement								$ 400,000,000		$ 400,000,000							$ 400,000,000
Number of extension maturity periods | Extension								2		2
Length of extension options										364 days
Debt obligations outstanding								$ 120,690,000		$ 120,690,000
10/30/2016 | Committed Loan repurchase facility
Committed Loan and Securities Repurchase Facilities
Committed amount on master repurchase agreement												$ 600,000,000				$ 600,000,000
Number of extension maturity periods | Extension												2				1
Length of extension options												12 months
Debt obligations outstanding												$ 229,533,000
10/24/2016 | Committed Loan repurchase facility
Committed Loan and Securities Repurchase Facilities
Committed amount on master repurchase agreement				$ 35,000,000								$ 35,000,000
Number of extension maturity periods | Extension				2								2
Length of extension options				6 months								6 months
Debt obligations outstanding												$ 575,000
Committed amount or master repurchase facility terminated	$ 35,000,000
5/24/2017 | Committed Loan repurchase facility
Committed Loan and Securities Repurchase Facilities
Committed amount on master repurchase agreement								$ 450,000,000		$ 450,000,000
Number of extension maturity periods | Extension		2						3		3
Length of extension options		1 year								12 months
Debt obligations outstanding								$ 187,031,000		$ 187,031,000
7/1/2018 | Term master repurchase agreement
Committed Loan and Securities Repurchase Facilities
Committed amount on master repurchase agreement								400,000,000		400,000,000			$ 400,000,000
Debt obligations outstanding								380,319,000		380,319,000
6/28/2019 | Committed Loan repurchase facility
Committed Loan and Securities Repurchase Facilities
Committed amount on master repurchase agreement								100,000,000		100,000,000				$ 100,000,000
Debt obligations outstanding								0		0
8/2/2019 | Committed Loan repurchase facility
Committed Loan and Securities Repurchase Facilities
Committed amount on master repurchase agreement	$ 100,000,000							$ 100,000,000		$ 100,000,000
Number of extension maturity periods | Extension	1							1		1
Length of extension options	12 months									12 months
Debt obligations outstanding								$ 37,944,000		$ 37,944,000
Number of additional extension maturity periods | Extension	2							2		2
Length of additional extension maturity periods	6 months									6 months
Credit and Security Agreement
Borrowing Under Credit Facilties and Debt Issuance Costs [Abstract]
Debt instrument, aggregate amount					$ 46,750,000
Credit and Security Agreement | One-Month LIBOR
Borrowing Under Credit Facilties and Debt Issuance Costs [Abstract]
Basis spread on variable rate (as a percent)					1.85%
Credit Agreement and Revolving Credit Facility
Borrowing Under Credit Facilties and Debt Issuance Costs [Abstract]
Unamortized debt issuance costs								$ 1,900,000		$ 1,900,000		3,400,000
Credit Agreement
Borrowing Under Credit Facilties and Debt Issuance Costs [Abstract]
Committed amount on credit agreement							$ 50,000,000
Number of multiple committed financing counterparties | Financing_Counterparty							1
Mortgage loan financing
Committed Loan and Securities Repurchase Facilities
Number of agreements | agreement										10	36
Mortgage Loans on Real Estate [Abstract]
Borrowing under credit and security agreement								575,500,000		$ 575,500,000
Mortgage loan financing												544,700,000
Net unamortized premiums								5,600,000		5,600,000		6,100,000
Amortization of premiums								200,000	$ 200,000	700,000	$ 700,000
Pledged assets, real estate and lease intangibles, net								$ 746,100,000		$ 746,100,000		$ 711,100,000
Mortgage loan financing | Minimum
Borrowings from Federal Home Loan Bank (FHLB) [Abstract]
Stated interest rate on debt instrument (as a percent)								4.25%		4.25%
Mortgage loan financing | Maximum
Borrowings from Federal Home Loan Bank (FHLB) [Abstract]
Stated interest rate on debt instrument (as a percent)								6.75%		6.75%
Borrowings from the Federal Home Loan Bank | Tuebor
Borrowing Under Credit Facilties and Debt Issuance Costs [Abstract]
Debt borrowings term										8 years		8 years
Borrowings from Federal Home Loan Bank (FHLB) [Abstract]
Maximum advance limit			$ 2,900,000,000
FHLB borrowings outstanding								$ 1,800,000,000		$ 1,800,000,000		$ 1,900,000,000
Additional committed term financing available from FHLB								$ 406,300,000		$ 406,300,000		$ 380,400,000
Weighted average term										2 years 4 months 13 days		1 year 5 months 1 day
Weighted average interest rate								1.05%		1.05%		0.84%
Maximum percent of FHLB advances to total assets															40.00%
Borrowings from the Federal Home Loan Bank | Tuebor | Ladder Capital Corp
Borrowings from Federal Home Loan Bank (FHLB) [Abstract]
Advance rates of total assets (as a percent)			40.00%
Advance rates of total equity (as a percent)			150.00%
Borrowings from the Federal Home Loan Bank | Tuebor | Minimum
Borrowing Under Credit Facilties and Debt Issuance Costs [Abstract]
Advance rates (as a percent)										61.00%		58.70%
Borrowings from Federal Home Loan Bank (FHLB) [Abstract]
Stated interest rate on debt instrument (as a percent)								0.38%		0.38%		0.28%
Borrowings from the Federal Home Loan Bank | Tuebor | Maximum
Borrowing Under Credit Facilties and Debt Issuance Costs [Abstract]
Advance rates (as a percent)										95.20%		95.20%
Borrowings from Federal Home Loan Bank (FHLB) [Abstract]
Stated interest rate on debt instrument (as a percent)								3.02%		3.02%		2.74%
Borrowings from the Federal Home Loan Bank | Tuebor | CMBS and U.S. Agency Securities
Borrowings from Federal Home Loan Bank (FHLB) [Abstract]
Collateral for debt instrument								$ 1,600,000,000		$ 1,600,000,000		$ 1,700,000,000
Borrowings from the Federal Home Loan Bank | Tuebor | First mortgage commercial real estate loans
Borrowings from Federal Home Loan Bank (FHLB) [Abstract]
Collateral for debt instrument								$ 770,600,000		$ 770,600,000		$ 568,200,000