FAIR VALUE MEASUREMENTS - Schedule of Carrying Amounts and the Fair Values of the Company's Financial Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Financial assets:
Cash and cash equivalents	$ 193,695	$ 191,218	$ 50,745	$ 118,756
Restricted cash	16,991	6,677	9,313	9,861
Pledged securities	102,059	97,859	$ 86,900	$ 84,850
Loans held for sale	787,552	951,829
Loans held for investment, net	59,886	66,510
Derivative assets	20,417	10,357
Financial liabilities:
Derivative liabilities	7,455	1,850
Warehouse notes payable	802,496	937,769
Note payable	163,781	163,858
Carrying Amount
Financial assets:
Cash and cash equivalents	193,695	191,218
Restricted cash	16,991	6,677
Pledged securities	102,059	97,859
Loans held for sale	787,552	951,829
Loans held for investment, net	59,886	66,510
Derivative assets	20,417	10,357
Total financial assets	1,180,600	1,324,450
Financial liabilities:
Derivative liabilities	7,455	1,850
Warehouse notes payable	802,496	937,769
Note payable	163,781	163,858
Total financial liabilities	973,732	1,103,477
Fair Value
Financial assets:
Cash and cash equivalents	193,695	191,218
Restricted cash	16,991	6,677
Pledged securities	102,059	97,859
Loans held for sale	787,552	951,829
Loans held for investment, net	60,157	66,963
Derivative assets	20,417	10,357
Total financial assets	1,180,871	1,324,903
Financial liabilities:
Derivative liabilities	7,455	1,850
Warehouse notes payable	804,201	939,500
Note payable	165,947	166,223
Total financial liabilities	$ 977,603	$ 1,107,573