EMPLOYEE BENEFIT PLAN - Net periodic benefit cost and related components (Details) - Multiple Employers Retirement Income Plan - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 502	$ 474	$ 1,004	$ 948
Expected return on plan assets	(532)	(565)	(1,066)	(1,130)
Amortization of net losses	199	198	399	396
Net periodic benefit cost	$ 169	$ 107	$ 337	$ 214