SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Cash Flows (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents
Cash and cash equivalents	$ 81,531	$ 191,218	$ 53,338	$ 118,756
Restricted cash	29,986	6,677	15,768	9,861
Pledged cash and cash equivalents	58,310	88,785	90,301	82,742
Total cash, cash equivalents, restricted cash, and restricted cash equivalents	$ 169,827	$ 286,680	$ 159,407	$ 211,359