FAIR VALUE MEASUREMENTS - Summary of Financial Assets and Financial Liabilities Measured at Fair Value on a Recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Assets
Loans held for sale	$ 1,257,256	$ 951,829
Pledged securities	105,803	97,859	$ 92,401	$ 84,850
Derivative assets	26,632	10,357
Liabilities
Derivative liabilities	8,669	1,850
Recurring
Assets
Loans held for sale	1,257,256	951,829
Pledged securities	105,803	97,859
Derivative assets	26,632	10,357
Total financial assets	1,389,691	1,060,045
Liabilities
Derivative liabilities	8,669	1,850
Total financial liabilities	8,669	1,850
Level 1 | Recurring
Assets
Pledged securities	58,310	88,785
Total financial assets	58,310	88,785
Level 2 | Recurring
Assets
Loans held for sale	1,257,256	951,829
Pledged securities	47,493	9,074
Total financial assets	1,304,749	960,903
Level 3 | Recurring
Assets
Derivative assets	26,632	10,357
Total financial assets	26,632	10,357
Liabilities
Derivative liabilities	8,669	1,850
Total financial liabilities	$ 8,669	$ 1,850