EMPLOYEE BENEFIT PLANS - Benefit Obligations, Plan Assets and Reported Amounts (Details) - Pension Plan - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Change in benefit obligations:
Benefit obligations at beginning of year	$ 109,626	$ 85,662
Service cost	2,473	2,174	$ 2,783
Interest cost	4,296	4,074	3,640
Actuarial (gain) loss	(6,420)	19,841
Benefits paid	(2,499)	(2,125)
Benefit obligations at end of year	107,476	109,626	85,662
Change in plan assets:
Fair value of plan assets at beginning of year	69,521	67,480
Employer contribution	3,116	2,671
Actual return on plan assets	(1,693)	1,495
Benefits paid	(2,499)	(2,125)
Fair value of plan assets at end of year	68,445	69,521	$ 67,480
Funded status at the end of year	(39,031)	(40,105)
Amounts recognized in balance sheet:
Non-current liability	(39,031)	(40,105)
Total amounts recognized in balance sheet	(39,031)	(40,105)
Amounts recognized in accumulated other comprehensive income consist of:
Net actuarial loss	$ (38,787)	$ (41,278)