FAIR VALUE MEASUREMENTS - Schedule of Carrying Amounts and the Fair Values of the Company's Financial Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Financial assets:
Cash and cash equivalents	$ 65,641	$ 90,058	$ 165,062	$ 191,218
Restricted cash	9,138	20,821	16,226	6,677
Pledged securities	120,302	116,331	$ 109,062	$ 97,859
Loans held for sale	1,259,075	1,074,348
Loans held for investment, net	454,430	497,291
Derivative assets	25,554	35,536
Financial liabilities:
Derivative liabilities	17,726	32,697
Warehouse notes payable	1,263,036	1,161,382
Note payable	294,255	296,010
Carrying Amount
Financial assets:
Cash and cash equivalents	65,641	90,058
Restricted cash	9,138	20,821
Pledged securities	120,302	116,331
Loans held for sale	1,259,075	1,074,348
Loans held for investment, net	454,430	497,291
Derivative assets	25,554	35,536
Total financial assets	1,934,140	1,834,385
Financial liabilities:
Derivative liabilities	17,726	32,697
Secured borrowings	70,052	70,052
Warehouse notes payable	1,263,036	1,161,382
Note payable	294,255	296,010
Total financial liabilities	1,645,069	1,560,141
Fair Value
Financial assets:
Cash and cash equivalents	65,641	90,058
Restricted cash	9,138	20,821
Pledged securities	120,302	116,331
Loans held for sale	1,259,075	1,074,348
Loans held for investment, net	456,928	503,549
Derivative assets	25,554	35,536
Total financial assets	1,936,638	1,840,643
Financial liabilities:
Derivative liabilities	17,726	32,697
Secured borrowings	70,052	70,052
Warehouse notes payable	1,263,314	1,162,791
Note payable	297,750	300,000
Total financial liabilities	$ 1,648,842	$ 1,565,540