COMPREHENSIVE INCOME (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
COMPREHENSIVE INCOME [Abstract]
Unrealized gains (losses) arising during holding period, Before tax amount	$ 5,956	$ (8,653)	$ 20,125	$ 380
Reclassification adjustment for net gains realized in net income, Before tax amount	(86)	(41)	(88)	(55)
Recognized employee benefit plan net periodic benefit cost, Before tax amount	1,511	1,797	3,022	3,594
Other comprehensive income (loss), Before tax amount	7,381	(6,897)	23,059	3,919
Unrealized gains (losses) arising during holding period, Tax effect	(2,279)	3,313	(7,699)	(168)
Reclassification adjustment for net gains realized in net income, Tax effect	33	16	34	21
Recognized employee benefit plan net periodic benefit cost, Tax effect	(578)	(687)	(1,156)	(1,374)
Other comprehensive income (loss), Tax effect	(2,824)	2,642	(8,821)	(1,521)
Unrealized gains (losses) arising during holding period, Net of tax amount	3,677	(5,340)	12,426	212
Reclassification adjustment for net gains realized in net income, Net of tax amount	(53)	(25)	(54)	(34)
Recognized employee benefit plan net periodic benefit cost, Net of tax amount	933	1,110	1,866	2,220
Other comprehensive income (loss), net of tax	4,557	(4,255)	14,238	2,398
Net income	34,692	39,713	57,241	71,979
Comprehensive income	$ 39,249	$ 35,458	$ 71,479	$ 74,377