COMPREHENSIVE INCOME (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Before Tax Amount [Abstract]
Unrealized gains arising during holding period, Before tax	$ 14,169	$ 9,033
Reclassification adjustment for net gains realized in net income, Before tax amount	(2)	(14)
Recognized employee benefit plan net periodic benefit cost, Before tax amount	1,511	1,797
Other comprehensive (loss) income, Before tax amount	15,678	10,816
Tax Effect [Abstract]
Unrealized (losses) gains arising during holding period, Tax effect	(5,420)	(3,481)
Reclassification adjustment for net gains realized in net income, Tax effect	1	5
Recognized employee benefit plan net periodic benefit cost, Tax effect	(578)	(687)
Other comprehensive (loss) income, Tax effect	(5,997)	(4,163)
Net of Tax Amount [Abstract]
Unrealized gains arising during holding period, net of tax	8,749	5,552
Reclassification adjustment for net gains realized in net income, Net of tax amount	(1)	(9)
Recognized employee benefit plan net periodic benefit cost, Net of tax amount	933	1,110
Other comprehensive income, net of tax	9,681	6,653
Net income	22,549	32,266
Comprehensive income	$ 32,230	$ 38,919