ACCUMULATED OTHER COMPREHENSIVE INCOME OR LOSS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Summary of changes in accumulated other comprehensive income or loss by component, net of tax [Roll Forward]
Balance at beginning of period	$ (8,785)	$ 155	$ (2,807)
Other comprehensive loss before reclassification	(2,788)	(5,075)	2,006
Amounts reclassified from accumulated other comprehensive income (loss)	631	(3,865)	956
Net current period other comprehensive loss	(2,157)	(8,940)	2,962
Balance at end of period	(10,942)	(8,785)	155
Total impairment losses	0	0	29
Net gains on securities transactions	372	6,869	16
Pension and other employee benefits	5,908	5,733	5,939
Income tax expense (benefit)	4,658	3,709	3,822
Net of tax	9,433	8,157	8,731
Reclassification out of Accumulated Other Comprehensive Income (loss)
Summary of changes in accumulated other comprehensive income or loss by component, net of tax [Roll Forward]
Net of tax	631	(3,865)	956
Accumulated Net Unrealized Investment Gain (Loss)
Summary of changes in accumulated other comprehensive income or loss by component, net of tax [Roll Forward]
Balance at beginning of period	1,960	6,043	8,023
Other comprehensive loss before reclassification	(1,520)	146	(1,988)
Amounts reclassified from accumulated other comprehensive income (loss)	(230)	(4,229)	8
Net current period other comprehensive loss	(1,750)	(4,083)	(1,980)
Balance at end of period	210	1,960	6,043
Accumulated Net Unrealized Investment Gain (Loss) | Reclassification out of Accumulated Other Comprehensive Income (loss)
Summary of changes in accumulated other comprehensive income or loss by component, net of tax [Roll Forward]
Total impairment losses			29
Net gains on securities transactions	(372)	(6,869)	(16)
Income tax expense (benefit)	142	2,640	(5)
Net of tax	(230)	(4,229)	8
Accumulated Defined Benefit Plans Adjustment
Summary of changes in accumulated other comprehensive income or loss by component, net of tax [Roll Forward]
Balance at beginning of period	(10,745)	(5,888)	(10,830)
Other comprehensive loss before reclassification	(1,268)	(5,221)	3,994
Amounts reclassified from accumulated other comprehensive income (loss)	861	364	948
Net current period other comprehensive loss	(407)	(4,857)	4,942
Balance at end of period	(11,152)	(10,745)	(5,888)
Accumulated Defined Benefit Plans Adjustment | Reclassification out of Accumulated Other Comprehensive Income (loss)
Summary of changes in accumulated other comprehensive income or loss by component, net of tax [Roll Forward]
Income tax expense (benefit)	(533)	(227)	(593)
Net of tax	861	364	948
Net Prior Service Cost (Credit) | Reclassification out of Accumulated Other Comprehensive Income (loss)
Summary of changes in accumulated other comprehensive income or loss by component, net of tax [Roll Forward]
Pension and other employee benefits	(90)	(90)	(83)
Net Unamortized Gain (Loss) | Reclassification out of Accumulated Other Comprehensive Income (loss)
Summary of changes in accumulated other comprehensive income or loss by component, net of tax [Roll Forward]
Pension and other employee benefits	$ 1,484	$ 681	$ 1,624