EMPLOYEE BENEFIT PLAN - Net periodic benefit cost and related components (Details) - Multiple Employers Retirement Income Plan - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 502	$ 474	$ 1,505	$ 1,422
Expected return on plan assets	(533)	(565)	(1,599)	(1,695)
Amortization of net losses	200	198	599	594
Net periodic benefit cost	$ 169	$ 107	$ 505	$ 321