STOCKHOLDERS' EQUITY AND ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Changes in Accumulated Other Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013	Dec. 31, 2012
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Unrealized and realized gains and losses on available-for-sale securities	$ 413		$ (57)	$ (268)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Unrealized and realized gains and losses on available-for-sale securities	269	[1]
Other Income [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, before Tax	269	[1]
Postretirement Medical Benefits [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss), Net Gain (Loss), before Tax	653	[1],[2]
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss), Net Prior Service Cost, before Tax	(635)	[1],[2]
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, before Tax	18	[1]
Pension Benefits [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss), Net Gain (Loss), before Tax	$ 983	[1],[3]

[1] Amounts in parentheses indicate debits to income/loss.

[2] These accumulated other comprehensive income components are included in the computation of net periodic postretirement medical cost.

[3] These accumulated other comprehensive income components are included in the computation of net periodic pension cost.