PENSION AND POSTRETIREMENT WELFARE PLANS - Pension Plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net amount recognized in the consolidated balance sheet
Accrued pension cost at end of period	$ 2,785	$ 3,142
Pension Plan
Pension plan
Number of last years of employment in which the employee's compensation is considered for determining benefits	3 years
Change in projected benefit obligation:
Accumulated post retirement benefit obligation at beginning of period	$ 6,950	5,738
Service cost	105	83	$ 103
Employee contributions	17	12
Interest cost	273	266	241
Actuarial (gain) loss	(391)	1,131
Benefits paid	(278)	(280)
Accumulated post retirement benefit obligation at end of period	6,676	6,950	5,738
Change in plan assets:
Fair value of plan assets at beginning of period	5,095	4,847
Actual return on plan assets	(52)	273
Employee contributions	17	12
Employer contributions	204	243
Benefits and expenses paid	(278)	(280)
Fair value of plan assets at end of period	4,986	5,095	$ 4,847
Net amount recognized in the consolidated balance sheet
Excess of projected benefit obligation over fair value of plan assets	1,690	1,855
Unrecognized loss	(1,823)	(2,028)
Accrued pension cost prior to pension adjustments	(133)	(173)
Accumulated Other Comprehensive Income at Current Measurement Date	1,823	2,028
Accrued pension cost at end of period	1,690	1,855
Accumulated benefit obligation	6,473	$ 6,697
Amount of accumulated other comprehensive income expected to be recognized as a plan expense in next fiscal year	$ 170