FAIR VALUE MEASUREMENTS - Summary of Financial Assets and Financial Liabilities Measured at Fair Value on a Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Assets
Loans held for sale	$ 787,552	$ 951,829
Pledged securities	102,059	97,859	$ 86,900	$ 84,850
Derivative assets	20,417	10,357
Liabilities
Derivative liabilities	7,455	1,850
Recurring
Assets
Loans held for sale	787,552	951,829
Pledged securities	102,059	97,859
Derivative assets	20,417	10,357
Total financial assets	910,028	1,060,045
Liabilities
Derivative liabilities	7,455	1,850
Total financial liabilities	7,455	1,850
Level 1 | Recurring
Assets
Pledged securities	74,445	88,785
Total financial assets	74,445	88,785
Level 2 | Recurring
Assets
Loans held for sale	787,552	951,829
Pledged securities	27,614	9,074
Total financial assets	815,166	960,903
Level 3 | Recurring
Assets
Derivative assets	20,417	10,357
Total financial assets	20,417	10,357
Liabilities
Derivative liabilities	7,455	1,850
Total financial liabilities	$ 7,455	$ 1,850