COMPREHENSIVE INCOME (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
COMPREHENSIVE INCOME [Abstract]
Unrealized gains (losses) arising during holding period, Before tax amount	$ 474	$ 14,169
Reclassification adjustment for net gains realized in net income, Before tax amount	(1,071)	(2)
Recognized employee benefit plan net periodic benefit cost, Before tax amount	1,533	1,511
Other comprehensive income (loss), Before tax amount	936	15,678
Unrealized gains (losses) arising during holding period, Tax effect	(183)	(5,420)
Reclassification adjustment for net gains realized in net income, Tax effect	410	1
Recognized employee benefit plan net periodic benefit cost, Tax effect	(586)	(578)
Other comprehensive income (loss), Tax effect	(359)	(5,997)
Unrealized gains (losses) arising during holding period, Net of tax amount	291	8,749
Reclassification adjustment for net gains realized in net income, Net of tax amount	(661)	(1)
Recognized employee benefit plan net periodic benefit cost, Net of tax amount	947	933
Other comprehensive income (loss), net of tax	577	9,681
Net income	38,093	22,549
Comprehensive income	$ 38,670	$ 32,230