EMPLOYEE BENEFIT PLAN - Unrealized gains, net (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
SERP
Defined Benefit Plan Disclosure [Line Items]
Unrealized gains, net	$ 785	$ 871	$ 3,636	$ 385

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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