EMPLOYEE BENEFIT PLAN - Unrealized gains, net (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
SERP
Defined Benefit Plan Disclosure [Line Items]
Unrealized gains, net	$ 370	$ 861	$ 4,006	$ 1,246

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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