VARIABLE INTEREST ENTITIES - Narrative (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) Loan	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)	Mar. 02, 2017 USD ($)
Variable Interest Entity [Line Items]
Carrying Amount	$ 1,658,862,000		$ 1,658,862,000		$ 1,726,283,000
Primary beneficiary
Variable Interest Entity [Line Items]
Maximum exposure to loss	68,200,000.0		$ 68,200,000.0
Floating Rate Notes, Weighted Average Coupon Rate, LIBOR Plus 1.85%
Variable Interest Entity [Line Items]
Number of properties collateralized for mortgage loan | Loan			12
Collateral amount	286,300,000		$ 286,300,000		$ 341,200,000
Receivables related to repayments of outstanding principal	$ 54,900,000		$ 54,900,000
Offered Certificates
Variable Interest Entity [Line Items]
Prepayment fee, percent	1.00%		1.00%
Mortgaged Assets
Variable Interest Entity [Line Items]
Prepayment fee, percent	1.00%		1.00%
Interest expense	$ 2,700,000	$ 2,100,000	$ 7,600,000	$ 4,700,000
Parent Company | Offered Certificates
Variable Interest Entity [Line Items]
Preferred equity fully funded amount						$ 32,400,000
Parent Company | Secured funding agreements and securitizations debt
Variable Interest Entity [Line Items]
Carrying Amount						68,200,000
Holdco | Mortgaged Assets
Variable Interest Entity [Line Items]
Principal amount of certificates retained by wholly owned subsidiary of the entity						35,800,000
ACRE Commercial Mortgage 2017-FL3 Ltd And ACRE Commercial Mortgage 2017-FL3 LLC | Floating Rate Notes, Weighted Average Coupon Rate, LIBOR Plus 1.85%
Variable Interest Entity [Line Items]
Carrying Amount						$ 308,800,000