DEBT - Summary of Mortgage Warehouse Borrowings (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Line of Credit Facility [Line Items]
Amount Drawn	$ 154,109,000	$ 123,233,000
Secured Debt
Line of Credit Facility [Line Items]
Amount Drawn	154,109,000	123,233,000
Facility Amount	280,000,000	230,000,000
Mortgage borrowings outstanding, collateralized amount	208,200,000	190,900,000
Collateralized amount of restricted short-term investments	3,300,000	1,600,000
Secured Debt | Warehouse A
Line of Credit Facility [Line Items]
Amount Drawn	16,594,000	25,074,000
Facility Amount	$ 25,000,000	45,000,000
Secured Debt | Warehouse A | LIBOR
Line of Credit Facility [Line Items]
Interest Rate	1.75%
Secured Debt | Warehouse B
Line of Credit Facility [Line Items]
Amount Drawn	$ 47,150,000	38,481,000
Facility Amount	$ 50,000,000	85,000,000
Secured Debt | Warehouse B | LIBOR
Line of Credit Facility [Line Items]
Interest Rate	1.75%
Secured Debt | Warehouse C
Line of Credit Facility [Line Items]
Amount Drawn	$ 66,865,000	59,678,000
Facility Amount	$ 75,000,000	$ 100,000,000
Secured Debt | Warehouse C | LIBOR
Line of Credit Facility [Line Items]
Interest Rate	1.70%
Warehouse D | Secured Debt
Line of Credit Facility [Line Items]
Amount Drawn	$ 13,875,000
Facility Amount	$ 60,000,000
Warehouse D | Secured Debt | LIBOR
Line of Credit Facility [Line Items]
Interest Rate	1.75%
Warehouse E | Secured Debt
Line of Credit Facility [Line Items]
Amount Drawn	$ 9,625,000
Facility Amount	$ 70,000,000
Warehouse E | Secured Debt | LIBOR
Line of Credit Facility [Line Items]
Interest Rate	1.875%