SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Statement of Cash Flows (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Cash and cash equivalents	$ 53,338	$ 118,756	$ 60,993	$ 136,988
Restricted cash	15,768	9,861	17,611	5,306
Pledged securities, at fair value	92,401	84,850	78,491	72,190
Total cash, cash equivalents, restricted cash, and restricted cash equivalents	$ 161,507	$ 213,467	$ 157,095	$ 214,484