COMPREHENSIVE INCOME (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
COMPREHENSIVE INCOME [Abstract]
Unrealized gains (losses) arising during holding period, Before tax amount	$ (11,169)	$ 6,225	$ 8,956	$ 6,605
Reclassification adjustment for net gains realized in net income, Before tax amount	(1)	(33)	(89)	(88)
Recognized employee benefit plan net periodic benefit cost, Before tax amount	1,511	1,797	4,533	5,391
Other comprehensive income (loss), Before tax amount	(9,659)	7,989	13,400	11,908
Unrealized gains (losses) arising during holding period, Tax effect	4,275	(2,382)	(3,424)	(2,550)
Reclassification adjustment for net gains realized in net income, Tax effect		13	34	34
Recognized employee benefit plan net periodic benefit cost, Tax effect	(578)	(687)	(1,734)	(2,061)
Other comprehensive income (loss), Tax effect	3,697	(3,056)	(5,124)	(4,577)
Unrealized gains (losses) arising during holding period, Net of tax amount	(6,894)	3,843	5,532	4,055
Reclassification adjustment for net gains realized in net income, Net of tax amount	(1)	(20)	(55)	(54)
Recognized employee benefit plan net periodic benefit cost, Net of tax amount	933	1,110	2,799	3,330
Other comprehensive income (loss), net of tax	(5,962)	4,933	8,276	7,331
Net income	37,817	34,343	95,058	106,322
Comprehensive income	$ 31,855	$ 39,276	$ 103,334	$ 113,653