DEBT - Summary of Mortgage Warehouse Borrowings (Detail) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Line of Credit Facility [Line Items]
Amount Drawn	$ 56,051,000	$ 130,353,000
Secured Debt
Line of Credit Facility [Line Items]
Amount Drawn	56,051,000	130,353,000
Facility Amount	170,000,000	230,000,000
Mortgage borrowings outstanding, collateralized amount	108,600,000	181,900,000
Collateralized amount of restricted short-term investments	1,100,000	1,600,000
Secured Debt | Warehouse A
Line of Credit Facility [Line Items]
Amount Drawn	13,962,000	29,484,000
Facility Amount	$ 45,000,000	$ 45,000,000
Expiration Date		30 days
Secured Debt | Warehouse A | LIBOR
Line of Credit Facility [Line Items]
Interest Rate	1.75%	1.75%
Secured Debt | Warehouse B
Line of Credit Facility [Line Items]
Amount Drawn	$ 18,899,000	$ 38,164,000
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	23,190,000	$ 62,705,000
Facility Amount	$ 75,000,000	$ 100,000,000
Secured Debt | Warehouse C | LIBOR
Line of Credit Facility [Line Items]
Interest Rate	1.95%	1.95%