ACCUMULATED OTHER COMPREHENSIVE LOSS (AOCL) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	[1]	$ (14,479)		$ (10,869)
Other comprehensive income before reclassifications		(186)		(4,269)
Amounts reclassified from AOCL	[2]	1,803		659
Other Comprehensive Income (Loss) - Net of Tax	[3],[4]	1,617		(3,610)		$ 2,416
Ending balance	[1]	$ (12,862)		$ (14,479)		$ (10,869)
Combined statutory tax rate		40.00%		40.00%		41.00%
Postretirement Liability Adjustment
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	[4]	$ (13,837)	[1]	$ (10,672)	[1]	$ (12,958)
Other comprehensive income before reclassifications		(110)		(4,345)
Amounts reclassified from AOCL	[2]	1,727		1,180
Other Comprehensive Income (Loss) - Net of Tax	[4]	1,617		(3,165)		2,286
Ending balance	[1],[4]	(12,220)		(13,837)		(10,672)
Unrealized Gain (Loss) on Derivatives-Other
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	[4]	(567)	[1]	(594)	[1]	(621)
Other comprehensive income before reclassifications		0		0
Amounts reclassified from AOCL	[2]	23		27
Other Comprehensive Income (Loss) - Net of Tax	[4]	23		27		27
Ending balance	[1],[4]	(544)		(567)		(594)
Unrealized Gain (Loss) on Available-for-Sale Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	[4]	(75)	[1]	397	[1]	294
Other comprehensive income before reclassifications		(76)		76
Amounts reclassified from AOCL	[2]	53		(548)
Other Comprehensive Income (Loss) - Net of Tax	[4]	(23)		(472)		103
Ending balance	[1],[4]	$ (98)		$ (75)		$ 397

[1] Determined using a combined statutory tax rate of 40% in 2015 and 2014.

[2] See table below.

[3] Determined using a combined statutory tax rate of 40% in each of 2015 and 2014 and 41% in 2013.

[4] Determined using a combined statutory tax rate of 40% in each of 2015 and 2014 and 41% in 2013.