FAIR VALUE MEASUREMENTS - Schedule of Carrying Amounts and the Fair Values of the Company's Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Financial assets:
Cash and cash equivalents	$ 191,218	$ 118,756	$ 136,988	$ 113,354
Restricted cash	6,677	9,861	5,306	13,854
Pledged securities	97,859	84,850	$ 72,190	$ 67,719
Loans held for sale	951,829	1,858,358
Loans held for investment, net	66,510	220,377
Derivative assets	10,357	61,824
Financial liabilities:
Derivative liabilities	1,850	4,396
Warehouse notes payable	937,769	1,990,183
Note payable	163,858	164,163
Carrying Amount
Financial assets:
Cash and cash equivalents	191,218	118,756
Restricted cash	6,677	9,861
Pledged securities	97,859	84,850
Loans held for sale	951,829	1,858,358
Loans held for investment, net	66,510	220,377
Derivative assets	10,357	61,824
Total financial assets	1,324,450	2,354,026
Financial liabilities:
Derivative liabilities	1,850	4,396
Warehouse notes payable	937,769	1,990,183
Note payable	163,858	164,163
Total financial liabilities	1,103,477	2,158,742
Fair Value
Financial assets:
Cash and cash equivalents	191,218	118,756
Restricted cash	6,677	9,861
Pledged securities	97,859	84,850
Loans held for sale	951,829	1,858,358
Loans held for investment, net	66,963	222,313
Derivative assets	10,357	61,824
Total financial assets	1,324,903	2,355,962
Financial liabilities:
Derivative liabilities	1,850	4,396
Warehouse notes payable	939,500	1,992,111
Note payable	166,223	167,327
Total financial liabilities	$ 1,107,573	$ 2,163,834