EMPLOYEE BENEFIT PLANS - Postretirement (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Estimated future benefit payments
2017	$ 513
2018	470
2019	516
2020	549
2021	590
2022 through 2026	$ 3,422
Postretirement benefit plans
Postretirement benefit plan disclosure
Assumed ultimate health care cost trend rate (as a percent)	3.00%
Accumulated benefit obligation after plan amendment	$ 12,128	$ 11,400
Amounts recognized in accumulated other comprehensive loss (pre-tax)
Prior service credit	(6,746)
Net actuarial gain	(1,846)
Net amount recognized in accumulated other comprehensive loss	(8,592)
Estimated amount to be amortized from accumulated other comprehensive loss (gain) into net periodic benefit cost during next fiscal year
Actuarial gain	236
Prior service credit	1,226
Changes in the accumulated postretirement benefit obligation
Benefit obligation, beginning of the period	11,400	12,311
Service cost	331	441	$ 342
Interest cost	462	465	423
Actuarial (gain)/loss	235	(1,580)
Benefits paid	(300)	(237)
Benefit obligation, end of the period	12,128	11,400	12,311
Net periodic postretirement benefit cost
Service cost benefits attributed to service during the period	331	441	342
Interest cost on the accumulated postretirement benefit obligation	462	465	423
Net amortization	(1,642)	(1,451)	(1,804)
Net periodic postretirement benefit cost (income)	$ (849)	$ (545)	$ (1,039)