EMPLOYEE BENEFIT PLAN - Net periodic benefit cost and related components (Details) - Multiple Employers Retirement Income Plan - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 490	$ 458
Expected return on plan assets	(650)	(709)
Amortization of net losses	230	206
Net periodic benefit cost (credit)	$ 70	$ (45)